I'm actually not sure about the file usage in comparison, but overall, Real is Proprietary, locked down, any program used to convert it is(technically) illegal, etc etc etc.
Even IF you do find a decent program/tutorial, the pain you'll go through searching just aint worth the 10MB difference.
I still don't understand why people use Real, the software is bloated, it's worse than a factory new Sony Vaio with bloatware, etcetcetc.
The only reason I see why people use real is because it's so locked down, my dad pays $10/month for a subscription to streaming Russian TV shows, and guess what format it's in? And guess what happened when my Grannie asked me to burn some episodes to DVD?
All in all, real's crap, the only time you ever wanna use it is 1)When you absolutely have to(Real Alternative) or 2) When you;re a corporationa dn want to lock yer shit down.