I think a man in a suit would be much better than a CGI creation. I don't care how good the CGI is, the actors are going to act better talking and interacting directly with someone on screen rather than someone holding a green pole with the Thing's head on it.
Well, that's not really fair, because present-day performance capture technology allows the actor to actually be there in the scene, interacting with the rest of the cast. For instance, when they did Lord of the Rings
, Andy Serkis did his capture work months after the fact and it was integrated with the rest, but on The Hobbit
, he was actually there performing the scenes with the other actors on the set or location, because the tech allows for that now. Same with other movies like John Carter
and The Avengers