I'm kind of in the same boat, trying to decide which Dressphere from Final Fantasy X-2 to do. [I eventually plan on doing every single one for Yuna]. What I usually do is see which one i like better, or when in doubt, print out pictures of them, put them on a dart board, close your eyes and throw it [or different ways, eenie meenie miney moe, etc].
As you said you could easily make/buy both of them, why not do both, esp if you're going to a three day convention, you can alternate them. Although you would have to buy two wigs, I think.
Wow, late reply is late
75% done [finishing up minor details]
....something! one of a couple ideas....
Back burner: Anima [FFX] 0% (figuring out HOW to make it ...)
Feel free to IM me about random crap, just be sure to tell me where you know me from