We've tried both diapers, and love both of them. FB don't have a smell issue that I'm aware of. If diapers begin to smell, then the type of detergent used is usually the culprit. I think most people feel you can usually get a better fit with three different size diapers (another words S, M, L Fuzzi Bunz) than a One-Size diaper like bumGenius. But bumGenius diapers seem to be the exception, and our experience has been that bumGenius diapers fit perfectly over a very large range, and actually better than FB do. But which one fits better will just depend on the build of your baby/toddler.
Fuzzi Bunz use snaps (long lasting), have a PUL outer layer (long lasting), a stain resistant inner fleece layer, and toddler proof snaps. Since there are two rows of snaps, one for the thighs and one for the waist, you can generally get a perfect fit every time (unless you have a low rise baby with really big thighs, LOL!).
bumGenius use velcro (may wear out over time), have a different outer that is more wick-free around the thighs, but needs to be washed on warm and line dried, and the inside can stain if it's not sprayed off right away. We will have leaks at night with our FB, but not with bumGenius because of the outer layer. But the outer layer does feel more plasticky, which some don't like, but pants slide over them really easily (big bonus for cloth diapers).
They're both great diapers! I'd really recommend trying a couple of each type before settling on one or the other. Good luck and have fun cloth diapering!