How you carry all that stuff you need to fly fish is rather a matter of personal choice. Each angler seems to have their own preferences and reasons for those preferences. I am a recent convert to the sling pack after having worn a waist pack for the past decade or so and a vest before that. I really like the sling pack but only came to that realization late this summer. Had I not had a buckle break on my waist pack, I might not have ever tried a sling pack.
My "perfect" vest or pack is light weight, cool and comfortable, and not too large. It is organized in a way that makes sense and the stuff I use most - forceps, tippet, floatant - are easy to access and stuff I use less commonly - leaders, thermometer, strike indicators - can be stowed away in less accessible places. Preferably the material used is at least weather-resistant if not waterproof. I will say in my experiences, waterproof fabrics are often rather stiff and I have had one waterproof pack where the seams just sort of fell apart eventually. Anyone that has backpacked understands that you will fill the space you are carrying. I prefer to minimize that space because you really do not need all that stuff. I prefer to travel light but organized. A good vest or pack keeps you from having to think much about where things are; accessing the stuff you need becomes second nature. A good pack should have places for things that are used often - tippet, nippers, floatant, and forceps - and places to tuck away the stuff you rarely use - extra leaders, strike indicators, tippet rings, and extra weight.
Here is what I carry with me on an average day of trout fishing:
3 to 5 spools of tippet (3X - 5X, maybe 6X and 2X)
a couple of extra leaders (including a few poly sinking leaders)
a few types of strike indicators and New Zealand strike indicator tool
Nippers
Forceps
Thermometer
Non-toxic split shot
fly floatant and desiccant
2 to 5 fly boxes
A net (not often enough...)
My current pack is the Orvis mini sling pack that I bought from the Driftless Angler for $79. Before that, I had an Umpqua waist pack which I used for about a dozen years. And prior to that, I used a vest. A fair bit of the time I carry little of this stuff and instead put a fly box in a shirt pocket, grab some 4X or 5X tippet, and clamp a forceps to my shirt and fish for a couple of hours. If there is one part I have had a hard time figuring out is how to best carry a net with me without it being in the way - vests seem to offer the best way to do that. It is nice if a pack or vest can carry a water bottle as well - otherwise I have it on a caribiner on my belt which is less than optimal.
Vests
Like many that have been fishing for twenty-plus years, I started with a vest. There really were not many other options. Vests seem to be much less commonly used by anglers today than a decade or two ago. Vests are a fine tool for carrying stuff. Vests can be a bit overkill - there is too much room to put stuff thus you are bound to carry too much stuff. Additionally most vests fit a fly box or maybe two per pocket so they become a memory game to remember which pocket that one fly box you need is in. Lastly, vests can wear rather heavy on your shoulders.
What I like best about vests are that they make carrying a net easy and they have a large back pocket which easily carries a rain jacket, a bit of lunch or an energy bar or two, and a bottle of water. Made of mesh, they can be lighter. And "shorty" or wading vests keep your stuff out of the water if you wade deeply - unlike waist packs - and they lighten the load a bit.
Waist Packs
I have used a waist pack for the last decade - the image below is what looks to be an updated version of the Umpqua pack I have. I liked the pack but the two biggest drawbacks were that it did not make carrying a net easy and it got dunked once in a while when I waded too deeply. Some do not care to have something around their waist - it wears like a heavy belt. And they can be a bit prone to getting fly lines caught on the accessories, buckles, and straps.
What I like about a waist pack is it is pretty out of the way and it fairly easily is spun around so I can access the pockets in it. And I was familiar with it, I knew where everything was located both inside the pockets and the stuff I had hanging from it. That is probably the biggest lesson here - packs and vests become part of you while fishing and one that works for you may not work well for others. You will be much happier with a pack that helps you organize all that stuff you think you need.
Chest Packs
Chest packs seem to be making a bit of a comeback. I remember fishing Pennsylvania where chest packs never left. The Richardson Chest Fly Box is a Pennsylvania tradition and are still made in Bellefonte, PA a city on the famed Spring Creek and Fisherman's Paradise. To me, they look like they have to be in the way for a fly angler but I have never used one. Older versions can, at times, be found on Ebay for hundreds of dollars. Their website provides testimonials from luminaries such as Joe Humphreys, Joan Wulff, Ed Shenk, Theo Bakelaar, and Robert Montgomery Knight (yes, that Bobby Knight). They are a neat piece of history though I know they would not be for me.
Image from: Richardson Chest Fly Box Company.
Today there are enough of them that Anchor Fly came up with a list of the best eight chest packs, none of which are the Richardson Chest Fly Box. I have an old Simms waterproof waist pack that I had dedicated to warmwater fishing but the seams recently busted out. I do not think I will replace it with another chest pack as it seems to get in the way more than other options do. Again, a lot of it is personal choice and what you have grown accustomed to. For me, the chest pack's downfalls outweigh their convenience of having everything readily accessible and "right there".
Sling Packs
I am new to sling packs but so far, so good. They are out of the way and the weight is well distributed. And the sling feature allows them to be easily accessible - sort of like a very temporary chest pack. When they "sling around", the zipped pockets are facing up and I can look down and see what I am looking for. The front strap is a handy place for nippers and hemostats. I bought the Orvis mini sling pack which I liked for the smaller size. So far, I really like my sling pack.
The downsides that I see are that I have not found a good way to carry a net on the pack (yet) and it can get a little warm on your back. It is nicely padded and is light and easy to carry but I still had a pretty good bit of "back sweat" after a day of fishing.
Backpacks
The next step up from a sling pack, backpacks can carry a lot of gear which is something I generally try to avoid. I have a really nice three year old backpack that is still functionally new Simms backpack that I won at a Trout Unlimited event. I say functionally new as I have put it on my back once and have never used it for more than hauling stuff in my vehicle. It will eventually get some use when I have a day I want to make a big day of it but it does not seem like a great option for daily use for all the reasons above - it's large, heavy, and hot.
Wrap up
First, I firmly believe that most people carry too much stuff that they do not need with them for a day on stream. I know, I used to be one of these people that had to carry at least half a dozen fly boxes and every gadget known to man. Honestly, most days I can throw a "curated" fly box in a shirt pocket, clamp a hemostats to that shirt, and go for a few hours. Most of the time, I do not need much more than that.
I like to have separate packs for smallmouth and trout. If I fished other species more often, I might have another pack or two. It is so much easier to have a pack ready to grab and go rather than switching gear out each time to use one pack Ultimately, I would probably like two different trout packs or a pack and a vest; one for standard trips and a larger one that I could put a lunch, rain jacket, a couple of water bottles, and other gear for longer days on the water.
A good pack or vest is a pretty minor investment and it is something that you will use all the time. I am hard on gear and I fish a lot more than most and I have gotten at least a decade out of every pack or vest I have owned. You can certainly pay more than the $79 I spent to buy a smaller Orvis pack but in any case, over a dozen or more years, that is a pretty small investment per year. Buy something that fits your style and needs. For me, I prefer to travel light; others carry a lot more "stuff" and will want to buy something larger. Packs and vests are a rather personal thing.
Each person has different needs and desires in a pack or vest. You may be looking for something much different than I am. For another point of view, watch the video above or visit the links below and let others know what you think and share your experiences.
Anchor Fly - Best Vests, Hip Packs, Chest Packs, Backpacks, and Sling Packs
The Wading List - Best Hip Packs, Sling Packs, Backpacks, and Vests
Orvis - Comparison of Different Packs
Fly Lords - Our 5 Favorite Fly Fishing Packs
Hatch Magazine - Reviews of Packs