I don't know how to choose a bike with the compact geometry (that's why I went to the LBS so they'd have to figure it out ).
I have an XS giant- I'm 5'3" and have a 30" inseam. I have an OCR1, and bought it with the intention of doing tris. The compact geometry is nice- and although the top tube is slanted I still manage to scratch it when I get on.
They make very nice quality bikes, IMO, and for the price you can't beat their reputation and durability!