yeah, you got it.
as far as i know they mostly have the same features, but some like this bios better than the other. so when you have decided what you like the best, you do not need to run several bioses on your chip anymore, of course.
just look at the feature-lists to get an idea of what every bios does (the cromwell for example does not run pirated code (done with the xdk), that's why many chips are delivered with that bios on them (because they are 100% legal then)).
Regards