FGU/A. Mark Ratner Space Marines - edition differences?

[Conquistador]

I have the yellow cover FanTac version and the follow-on FGU larger format version and (based on some comments made in an interview,) I skimmed both looking for possible game differences.  Other than minimal packaging differences and formatting, I don't see any changes right away.  I have family here for a visit but when that  is done I hope to read both version comparatively.  In the mean time, if you also have both versions, do you see any serious mechanics or background differences?

Gracias,

Glenn