Please help: CS PhD in Purdue vs Maryland,Park vs McGill

[RosaC]

Got BS and MS degree from the US. I'm torn between Purdue, the University of Maryland college park, and McGill cs PhD. All full fund. All have very interesting topics and good professors. Purdue and UMD have large groups and McGill is a small group. What's more, Purdue and UMD's advisors are professor while McGill's professor is an assistant professor. Personally like Montreal's life, but the other two schools seem to have a better reputation. Really need some advice. Thank you very much!