When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
I think the Si looks nicer off the bat with the front lip and colored sideskirts. It's also roomier inside (doesn't have a useless plastic tray in the middle of the rear seat). Insurance is also slightly cheaper on an Si.
BUT, like everyone else said, performance-wise, the GSR is a better platform to work with.