I was all set on buying an Avail 3. Then The Boyfriend, poking around on Performance, came across this.

So far, comparing the two:

Avail:
Pro: 1) Have ridden one and liked it.
2)WSD (possibly a plus) (boyfriend keeps saying it's not significant...)
3) It is rather prettier...
Con: more expensive ($750 is the lowest I've found)

R-330:
Pro: 1) Price
2) Better components (apparently. I don't know these things)
3) The boyfriend and his dad (both bike nuts) recommended this one
Con:
1) I have no actual idea what frame size I should be getting, and availability of certain frame sizes is limited
2)I'm not thrilled about the black.

Other than aesthetic reasons, I have misgivings about the R-330, and I don't know why, because I should be getting "more bike for the money."
Could someone qualitatively explain what the differences between (at least, Giant's versions) women's frame and the "men's", and what can't be solved by tweaking things and swapping out parts?
I'm pretty sure this has been asked before, but how does one go about (roughly) determining frame size?
Are there other things I'm not considering?