I haven't' bought a Bluetooth speaker, but these guys usually have really good comparisons and reviews on electronics like this:
http://thewirecutter.com/reviews/the-be ... h-speaker/
They liked the Logitech UE Mini Boom as the best. They compare it specifically to the JBL Flip, and tell you the pros and cons:
JBL’s Flip is yet another speaker that has great sound that’s lacking in other respects. It’s a touch larger than the UE, so it can deliver really punchy sound, as explained by Mike Calore at Wired and Jeremy Horowitz at iLounge. For many reviewers, it’s the best-sounding speaker $100 can buy. But a few convenience setbacks keep it from being as good as the UE. First of all, its 4-hour battery life is borderline unacceptable considering the competition. That’s less than half of the lifespan of the UE. As for ease-of-use, the Flip gets its name from its ability to be played while upright, or horizontal — unfortunately, its cylindrical design makes it prone to tipping in either position. It also has a proprietary charger with a big transformer on the end that has no place in the speaker’s included carrying case. At $100 on Amazon, we don’t think the boost in sound quality is worth the sacrifices in portability and ergonomics.
So JBL sounds better, but much worse battery and crappy charger. I guess choose based on what matters to you.