At this point, I think it's a matter of flipping a coin. Both are popular, but from what I understand Olaf is now using a Return Ticket system (instead of the pager system). So, it depends on whether you want an afternoon or evening return time for RSR (Olaf's M&G is indoors, so it won't look different in the daytime or nighttime). If you wanted an early RSR return time, I would head there first. If you wanted a later return time, I would go to Olaf first. RSR FPs are lasting longer now, but I would still aim to be there within the first 90 minutes of park opening. With Soarin' currently closed, it seems to have put more pressure back on RSR FPs (they were lasting up to 2 or 3 three hours, but lately it seems like 1.5 to 2 hours is more common).