Dynamic bars are the best, but not made yet (?). Simply make a gesture, and a bar will pop up close to your fingers. Then, it does not matter which side it is on, because it is on ALL sides!

Except for text entry, which pretty much needs to be horizontal, I prefer side bars on the tablet, because the tablet's screen has a lot more width than height.

That being said, I wish all of the bars and widgets would just go away when I'm not using them.