I've been on a pro angler, and the difference in stability between it and my kingfish it painfully obvious. The reason i like the pro is that i can store 6 rods in the side storage area, which is similar to a bass boat's rod locker, plus 2 in the vertical holders. On my yak, i can carry 4 on the holders on my crate and 2 more in the vertical molded-in holders. If i am flyfishing out of my current yak, i have to remain seated (not stable enough to stand in) and the vertically stored rods behind me impede my rang of casting. I love my kingfish for smaller waters and for the ease of transport, but trying to flyfish out of a more stable boat, being able to fish/fight fish while propelling myself, and having enough room to bring the gear needed to pursue multiple species with multiple techniques are my reasons for wanting a pedal-driven, larger craft.
For rivers and even stability, i think the Coosa is better than either the pro or the mariner, but given my preferences, the bigger craft are a better fit.