I also recommend just trying both of them. I prefer Bongos for several reasons.
1. It's easier to configure for me. This is obviously a personal preference, as others find BT3 easier to configure. I like the right-click menus in Bongos. I also like sticky bars that make them 'dock' to one another without my spending time trying to get them perfectly aligned. According to Sparr's post, this has been added to BT3 too.
2. Paging is easy to set up. I use three bars of buttons. (Don't panic, they're scaled down and don't take up tons of room.) On my rogues, I only need one bar to page. However, my druid has two bars that change for bear form, and a different two bars for kitty. It took me longer to figure out which buttons I wanted where than to figure out how to make them page. This is a Good Thing.
3. In tandem with above, copying profiles from one char to another is easy. This is nice when I start another toon on another server to play with a friend and just want to copy my existing bar setup.
4. Less fluff. I can't be specific as it's been a while since I used BT3, but I remember it having a lot of options that make me skeered.
They're both good mods. In the end, it's probably best if you give them both a shot and see which one works best for you.
