I am considering two different sizes of the same bike to purchase from bikesdirect.com and I want to make sure I have the right fit. However I am not of average proportions lol, so I am unclear whether to buy the XS or S size.

I'm 5'5", but have a longer torso and shorter legs. The XS has a more ideal seat tube length (though just barely at ZERO standover, but I can live with that), while the S offers a more preferable top tube length (with the downside being a negative standover clearance lol). Sheldon Brown says top tube length is more important than seat tube length, but I'm still unsure...

Should I go for the S or XS?

Here is the geometry sizing chart for the model in question:

http://www.bikesdirect.com/products/...e_geo_10_g.gif