I would say get a sponge filter. AquaClears are powerful filters with a lot of flow. I honestly can't see a 10 gal with two bettas needing something like that. Sponge filters will provide all the biological and mechanical filtration you need. They will also be significantly cheaper as a startup cost and long-term.
As for dividers, I wouldn't use the one at Petsmart. I had it before I made my own; it's completely see-through. Even with the double-divider you fish would be able to see each other. I made my own using craft mesh and report card binders.
As far as divided tanks, I love them!
I like the 3-section method because it gives a barrier to jumpers (it's already come in handy 2 times) and a visual barrier. I'm not kidding when I say I've found my one and only method of keeping bettas.
I've taken a big liking to plakats recently. I only have one right now, but I know I will have many more in the future. They are so full of energy! I love the long-finned halfmoons and vieltails, but if you want a ball of energy, get a plakat.