As I recall, the primary difference is the 222 HP (normal turbo) vs. the 240 HP (R). The R is much sportier and rides a little bit harsher but handles like a boxter. (Figurative of course) A T5 with the sport package (what I have) has 16" wheels (205 50 16) slightly lower ride height than that of a GLT, and a higher-pressure turbo. Add a set of 17" wheels, tighter handling, beautiful air dams, fog lamps, spoilers, 18 more HP, and an attitude to get the T5-R. Also the options package on the 850 Turbo and R include leather, auto tranny (5 speed in Canada), traction control, ABS, heated seats, electronic climate control with 2 zones, spoiler, headlight wipers, and more. I am not certain what all changes between the 850 Turbo and 850 R compared to the GLT and other models beyond what I have written above. If you plan on having a pretty normal family car that rides quiet and gentle, go with a GLT. If you do not mind having a flashy car, tight handling, a bit more noise, and an occasional harsh bump run with the R. For something in between go with an 850 turbo with sport package. Hope this helps, and make sure you drive each one before making a decision. Also, consider the cost of tires and maintenance of the different cars. I had to ban my last girl from driving my car as she likes to use the curb as a parking stop. 16" and 17" wheels do not like this treatment and are costly to repair and repalce. Also there is much less rubber between the road and wheel, so if there is a pot hole it can cost you more money if you hit it.