Iso+mp3 or CD on win Gens?

Playing ISO+Mp3 segacd-roms on Wingens 1.40b is better than playing by CD drive directly ? I form this question because i heard a lot of audio stutters playing Flashback CD (I love his the cinematic scenes), and other games. Thanks guys.
I think the explanation is that some CD readers hog the CPU more than others, so they take cycles away from the emulator.