i have the standard, open-caged bearings in my bottom bracket, and to be honest, i don't really care how well they're greased, as long as my cranks spin. unless you plan on pedaling the bike, it doesn't have to be all top of the line, sealed, etc.
on a motor bike, the BB hardly gets used, so if the bearings are a little gritty, i don't care. i've heard of some people actually over-tightening them so the cranks don't spin as easily.
obviously, this applies only to motored bikes. all my pedalers are super smooth.
an open, non-caged bearing is faster than a sealed bearing, as there's very little drag, but the trade-off is maintenance and bearing life.
in my coaster brakes i remove all the balls from the cages, then add more bearings so they spin super-awesome. this is kinda a pain in the a** but i don't really mind. my headset and BB are caged bearings, and they're actually 70 years old or so. and they still work fine.
it really comes down to how much maintenance you want to do, and what the quality of the hub, BB, headset, whatever you're using is. a cheap sealed bearing hub usually has cheap sealed bearings, so they're not much better than open bearings.
there's also a lot of high-end parts using ceramic bearings now. they ain't cheap.