Looking at the prices I find that if considering what you're getting for the dollar, the GXP is the way to go.
For $4500 you get:
18" rims & tires
Northtar V8 engine
GXP-only carbon fiber interior trim
GXP-only body cladding
GXP-only front bumper with projector driving lights
GXP-only floor mats
GXP-only red brake calipers (upgraded braking from SLE? -I'm unaware)
GXP-only exhaust with twin/twin exhaust tips
GXP-only 2-tone suede leather seating sufaces
GXP .... a whole lot more!