Hey Toddro..
excellent question! I was asking the same thing a couple of months ago, and through some good advice from Mike, Grumpy, and a few others, I ended up with a Jon.
Like you, I highly admire the River Hawk, it is a good solid and stable fly fishing boat....but, being on the retired side of income now, I elected to go with a used Jon and searched until I found exactly what I was looking for. A regular Jon, I don't think you would be happy with, they only have a 36" floor at best and are not stable enough to really fly fish from. I know lots of people that do, but I prefer the stability that my Lowe Big Jon gives me. the floor is a solid 48" wide and the widest point of the boat is a little over 6 feet. I built a casting deck in the front of it and it really does serve well, I was pretty pleased with it. I know that Mike will ring in with some great advice since he has the Hawk and he also has a Big Jon/