The reason AOG isn't known for certain, because juries don't or can't explain their decisions, but on the productions I've seen I would say that a conviction for McDonald would be very unsafe.
For a rape to be convicted one has to have lack of consent, and additionally lack of reasonable belief that there was consent. For McDonald it seems that he spent enough time with the woman who was, apparently, initiating proceedings that it does seem reasonable for him to believe that there was consent. For Ched Evans, whose arrival in the room was essentially instantaneously followed by sex, there are far fewer grounds for "reasonable belief" of consent. It's not enough to ask someone, especially if a) you've never met them and know knothing of their circumstances or mental state, b) they are naked on the bed and c) they are already having sex with someone else and so are in a vulnerable position.
Based on Ched Evans' own testimony I think it seems highly unlikely that he had reasonable belief of consent; whereas McDonald had gone through a taxi journey and long conversation with her. Again, I do not see an inconsistency.