My two cents - I would never use the Zune Software ripping software (or iTunes, for that matter). For Windows, would use EAC.
The reason is that it's more reliable -- if a CD is scratched or weathered, it could affect the rip and end up with errors. Usually small defects that can sometimes can be heard during playback. EAC is designed to deal with these defects and correct them.
You'd be surprised how many CD's I own that look fine cosmetically, but end up with errors during rips that need to be corrected. The optical drive could also be at fault, of course.