I have one styrofoam hive. It's great, I wish I had more. The bees that are in at are absolutely booming. It's packed with bees all the time. It's light weight, but it's still heavy when it's full of honey. I had to reverse twice this year, she just wasn't willing to move down. BUT, once spring rolls around, one of those bodies is usually empty and the other one is usually not completely full.
I think you will be easier with two bodies, but it's your choice.