Can someone educate me?

 

Single piece wheels come in so many flavors (various casting methods, cold/hot forged variations, etc.) I won't even touch the "this kind is better" because a) better for what, and b) totally depends on how either type is constructed.

Wheels using a cast, forged, or machine center can bolt on a rim rolled out of metal. It's not really correct to say this is a lighter wheel, etc., but you can reuse the same center as a manufacturer and create many variations by bolting on different rims. This saves them some money and allows more models, plus they do not have to worry about welding and finishing joints from spoke to rim.

In race track situations, this also allows the same center to support different width rims, although I'd like to know how many people actually do so!

Bottom line - IMHO people tend to go with what they like, and the bolt-on look esp. on larger diameter wheels.

Go with what you like, but understand how its made - and what tradeoffs you run into based on where you intend to use them!

SteveZ