Wider the boat, more contact area with the water, more drag = slower.
Bigger the boat, more weight, more inertia to get moving = slower.
You're talking a pretty wide range of boat sizes there. A 32" is going to fly, but it's not much more stable than a canoe.
Comparing a 9.9hp powered 1448 to a 1232 is almost like comparing a tug to a cigarette boat (~2x the weight & 75% more contact area on plane,) if the answer isn't obvious you probably shouldn't be on the water, it's safer for you that way
But seriously, the advantage/trade off is stability vs. speed/fuel economy & engine cost. Sure that 9.9 is fairly inexpensive and stingy on gas, but it's not going to launch a 1448 the way it will a 1232. Likewise, you can probably get a 30hp on the 1448, but it will cost you 3x as much and good luck carrying that rig over the boulders & down to a carry-only launch.
If you're seeing them all planing and topping out about the same you're probably seeing different sized motors on each or different weights. Jon boat hull weight vary greatly with the thickness of the aluminum from which they're made. A 1436LT from Alumacraft for instance weighs 140 lbs, whereas a std. 1436 from Alumacraft weighs 165lbs...(those may have changed slightly since my model year) - point being both are 14' long and 36" wide - even if it looks like apples and apples on Youtube it likely isn't. My buddies 6hp can plane a 1036 with his and my *** in the thing with all the gear and a TM on the front, but we're only doing maybe 8 ~ 10 mph. Without me and my crap he'll do 15 easily. Smaller the boat the more sensitive it will be to changes in weight.
Where do you fish (how busy is it, are there any restrictions etc.), what do you have (9.9 & no boat??) and what do you need (are you 400lbs and liable to swamp a 1232 if you sit on the rear bench with the motor & gas tank)? Figure those things out and find something to fit your needs.
If you're working around a 9.9 and just looking for something it can handle I think most people here would agree a 1236 or 1436 would do nicely with it provided you're not looking to tote around 750lbs worth of motor, gear, beer & fat fishermen...it'll move a 1448 too, just don't expect to win any speed contests.