For me, any pack or vest that puts the weight on my shoulders or upper back gives me a sore back at the end of a long day of fishing. I mainly wade fish small streams and do a lot of crouching, bending, etc. Every time I bend at the waist, I'm lifting the weight of the pack on my shoulders and after a long day, I feel it my back. For me a lumbar / waist pack works much better in reducing back soreness.

I do use a Fishpond product -- the Waterdance pack -- and love it. While they are a bit pricey, I think Fishpond has the best design, best quality, and best durability on the market.