Personally I saw that as Aeris trying to goad Tifa into confessing by putting her into awkward situations. Had Tifa gotten upset and made a scene, she would have finally been able to vent her feelings and get it off her chest. I saw it as an attempt at a good thing. But I can see how it could be the other way around. I think Aeris was just a big flirt really. I'm not positive she woulda went into a relationship with Cloud even if she could. I think she was just enjoying his company. But anyway, to the heart of the matter. Judging from people's responses on these topics I'd have to assume it's because Aeris is a goody-two-shoes. She tried to be too much of a goody-goody? Its not natural to be that uh... for lack of a better word, "pure". People see it as 'trying too hard' and assume she's not being herself. She's not "human" enough. It would have been interesting to see a bit of a bad side I suppose. Tifa on the other hand had the conflict of unrequited love throughout most of the game that most people can relate to which makes her very human to them. So naturally a lot of people would choose Tifa over Aeris on surface value. I have to admit though for some reason I was doing a lot of reading between the lines as far as Aeris was concerned. So I prefer Aeris, but not all if is based on things given at face value. So in the most literal sense, it's merely my opinion. :D

Edit: About the crying thing. I honestly don't remember either. But I could see her having feelings about Tseng being killed. She was always running from the Turks, but somehow she had developed a bond with them as well. Especially him. But its been too long since I played it for me to really remember.