okay so I think I finally figured out how I want to word my response. I know this will be picked apart and what not, but feh, I guess I should expect that here.
When I talk about how Aerith can get feelings and what not out of Cloud in a away that Tifa can't... I'm talking, first of all, about her special ability. She's able to see through Cloud and see what he's feeling and thinking. Think back to their date, she knew something was wrong with Cloud even though she barely knew him.
Tifa ALSO knew something was wrong with Cloud, but that's because she knew him and knew he was acting off.
Tifa understands Cloud the most because she knows him the best, and she's taken the time to try to understand him. She literally walked through his mind, feelings and memories. However, there are still moments when he confuses her. He might act strange, or do things like leave without notice or refuse to rescue his captured children. When Cloud did this, Tifa didn't quite know what was going on or how to react. At first she tried to be calm about it, but eventually she blew up at him, which is, IMO exactly what he needed. I won't deny that. I've often said I thought she went EASY on him.
As for how Aerith dealt with it... well I don't think she really got the chance. She spoke to him once when he was on his motorcycle, but Tifa had already taken care of it by then. I have no idea if she would have done it better, but I'm sure she would have dealt with it differently.
Aerith and Cloud had a great chemistry going. They only knew each other for a short time, but they really built up a great relationship. A relationship that at that time in the game, Cloud didn't share with anyone else. And I think that's important and that makes it very special.
So hopefully that explains where my previous post was coming from... it probably won't and I probably said something stupid again. But I'm in NO WAY trying to downplay Tifa, I'm just saying Aerith deserves a bit of credit too, if nothing else, for her ability to see though and get a glimpse of the real Cloud.