I go by a mix of colors, the included Legendary, and the Pokemon included. If one version has a specific Pokemon that I really like and the other doesn't, of course I'm going for the first one. Like with Red verses Blue, Red had Growlithe and I've always loved that thing - so Red was my choice (not that I didn't end up with both games, tho).
Hmm...ya know, the only time I ever did that was when I was deciding between Ruby and Sapphire. I thought Groudon was ugly at the time, and liked Latias better than Latios, and both Kyogre and Latias were in Sapphire, so I got it.
This time around, I'm not so sure. I think I like Parukia better than Diaruga, but I dunno if it's enough to make me pick Pearl. Plus...I may have a pattern going. The one's I got first were: Blue, Gold, Sapphire, (Fire Red). So, if you go by color, you go with Blue, Red, Blue, (Red), but if you go by order, you get two, one, two, (one). So which one do I go with? Diamond is blue, but comes first! Waaagh! And does FrLg even count in my pattern? CURSE YOU, NINTENDO AND GAMEFREAK! T_T
On topic, I think neither are all that masculine. Maybe Diamond, since it's color isn't pink...but sheesh! It's a game that either way is going to be named after a gem worn by women! *rolls eyes* I think you shouldn't base your decision on the masculinity of the game...that's a bit silly, in my humble opinion.
Although, I picked Diamond in the poll just because, so my "humble opinion" may be hypocritical. X3