Do you meen like sealed bearings? If you do, then they arent exposed. You dont need to grease them, they hold up a hell of alot better, they dont suck like unsealed bearings do and are better.
I think that he's referring to the bearings used by the old XS cranks and the Solid headset, actually, which are exposed and do require greasing. The advantage of them is them is that they don't crush or break very easily.
I'm not really thrilled with the Solid headset - I've had it for a couple of years (flatland) but it is a little bit difficult to adjust. The cap on top is supposed to lock in place to keep it from needing adjustment, but it is impossible to get it set up perfectly, then you do something hard on the bars, and it slips up or down and your fork gets loose or tight. I think the BEARINGS are good (needle), but the overall design is not my favorite.
I think I will get a sealed headset when I am motivated.
I have a King at them oment, and frankly I don't like it all that much. I'm planning on buying a Solid for when the King sh1ts the bed, and then warrantying the King and selling the replacement for a lower price.
You can't put different bearings into existing parts.
ie: If your hubs are designed to accept 5mm round ball bearings, that is all they will ever accept. You can't switch them out to needle bearings or sealed (cartridge) bearings either. You can only buy a new hub that is designed using sealed bearings.
Sealed bearings are the way to go with stuff if available in most instances. Hubs, bottom bracket for sure. Pedals? I don't use them there... Headset? Maybe, I have little experience with headsets & sealed bearings.
A lot of FSA headsets are available with needle bearings, but I have a Cane Creek ZS-2 and it is sweet. I probably won't ever get another headset that is not cartridge. As far as pedals, the last two pair that I have owned (Snafu OS and Wellgo MG-1) are cartridge, and I will probably never go back to looseball on those either. As a side note, the Mags are stinkin SWEET!
JMC - You typically buy cranks which will come with a sealed bottom bracket. Every good 3-piece crank comes with a sealed (cartridge bearing/roller bearing) bottom bracket. I've never heard the term roller bearing before and have only heard them called cartridge bearings.
To clarify, in the bicycle industry in general, there are looseball, needle, and cartridge bearings. People in the bmx world are often confused because some companies have what they call "Sealed mechanism headsets or bottom brackets". These aren't cartridge bearings. These are looseballs in cups with an extra piece of plastic or rubber between the bearings and the covers. So just watch out for what you are getting.