I debated back and forth over which device to get. Not only that, but also whether or not to get the one (from either BB or BM) that synced with smart phones. I ended up going with the BodyBugg SP (smart phone).
I absolutely love the BB, itself. But the iPhone application totally sucks. Also, the website BB lets you log your food on is just kind of bland and just not for me - I like bells and whistles and user-friendly-ness (that's totally not a word, but you get it!). All-in-all, I wish I would have gotten the Smart Phone version of the BMF (BodyMedia Fit). From what I researched, their website it better, their application is better and the BMF also logs your sleep efficiency.
I wanted the BMF in the first place, but I got my BB for $70 below retail with some smart couponing and waiting for a sale - and it also came with 10 free months of the online subscription.
Another thing to consider... If you're the kind of person who likes to see how much they've burned during a workout, I'd recommend the SP versions of either devices. It's nice to check while I'm at the gym how many calories I've burned and whether or not my workout is as effective as I think it is.
I could not say enough nice things about my BodyBugg. The device and what it does for me is amazing. But, honestly... I wish BodyMedia had offered the low price with the extended 10 month subscription because I would for sure have purchased that, instead. As a poor college student, I had to consider finances before what I truly wanted. Go with the BodyMedia Fit. The devices are pretty much identical - it's just about what fits with your wants and needs (and also, if you're like me, your budget!).
So... there you have it! I hope that was helpful. Just my two cents...