I just went through this debate myself and it cost me alot of $
I have my Simms Guide vest which I always liked and wore. I decided to go slimline and bought a Simms headwater waist pack Simms Headwater Waist Pack | Front Range Anglers | Boulder, Colorado Fly Fishing Shop and Guide Service
I will be honest I am not 100% in love with the waist pack other than I do alot of wet wading when it is warm. The hip pack is good and serviceable, just not great. Basically Ive ran into some "deeper" water and it does get wet causing moisture for my camera , wallet etc etc.For me if I am wearing waders I will always wear the vest.Mostly due to gravitational challenge. Waders accentuate my moobs (man boobs
) and therefore no pictures allowed.If I am wet wading ie shorts and tshirt I grab the hip pack, if it is warm enought to wet wade at 9000 feet, it is to warm to have a vest on too.
I do have both set up with forceps, nippers, floatant, leader and tippet. All I have to do is swap fishing license and fly boxes between the two, so that I dont leave anything at home.
Pros: carry multiple fly boxes , more pockets, gear to me stays drier , just more room in genereal
Cons: tend to carry way more than needed, to warm in the summer
Pros: light, comfy, easy to use , forces you to dial in your fly selection and carry one box. I now have spring, summer , fall fly boxes.
Cons: Not a lot of room to hang gadgets from so I put all of them inside (sometimes a pain) , can hang low and get wet.