I don't think you will see a functional difference in how they drain. From what I've heard, they handle a little different. DS floors are flat on the bottom side too, so the "keel" affect of I-beams goes away. The terminology is tracking, an I-beam floor is supposed to track better. Aire floors are I-beam too, but the I-beams are inside the floor pocket, so they are flat and slick on the bottom also. Personally, I haven't been able to tell much of a difference in tracking between the two. I don't fish, so take my opinion with a grain of salt. I think 14's are great overnight boats, and even paddle boats. I think 13's are great paddle raft boats, or light overnight boats. I think you could be happy with a 13 foot boat 95% of the time, and a few times you would want a little more capacity. Other than the extra cost of a 14' raft, I don't see much of disadvantage. The weight difference is minimal. Most 14' rafts fit 40" dry boxes and 40" coolers. Your passengers have more seat space. You can haul more weight and draft less water. You might want to rent some 13 and 14 foot rafts and see what fits you best. In fact, that might be money well spent. Making friends who boat helps a lot. Are there any clubs around your area? You can go with people and observe what works for them and what you might like for your own rig. I still learn. I still have a lot to learn. We all do.
Oh, I run a 14' Sotar ST raft year round. I row sometimes and paddle team sometimes. I have a wife and 2 kids. We can fit enough stuff for us for a few days right now, but my kids are young ( 5 and 7) and don't take up much space. I want a 13 just for paddling and keep my 14 for a rowing mostly. I don't fish from my boat, so I don't have much advice to give there, but plenty on the Buzz do.
Wishing I was on the river instead of surfing the web...