I think there is a big misconception about mason academics. The university is becoming less selective. The acceptance rate is 81%, the same as Radford. The president said he wants Mason to be a university for all people not the stereotypical college student (paraphrasing).
That's the New American University model. I'm not necessarily sold on it myself, but inflating your selectivity model the way Northeastern has doesn't necessarily make you a better school either.
As for academics and the students who go to the schools:
Radford average GPA 3.24, average SAT score is 1033
George Mason average GPA 3.66, average SAT score 1197
So, let's not necessarily look at how many get accepted, let's look at who is applying and being admitted to the university.
I also think you're going to have a higher acceptance rate, also, because of where GMU is located and the fact that it serves as a continuing education institution for local professionals. You aren't going to get that at a Radford or a JMU or a UVA or a Tech.