Hiya Kowboy! Welcome to our playpen...

You asked a couple of interesting questions; and none of them have any simple answers!

Fuel mileage?? That depends solely on what your right wrist does when your brain screams , "Go!"... Most folks seem to get around 30mpg, but ihat varies quite a bit. I average about 33mpg with my RT, but i drive like an Olphart...

Comfort? At 6'4" you'll want to sit on both the GS/RS and RT models to see how they fit you... The seating position on the RT is more touring oriented, so I'm guessing that it'll give you more of a chance to spread out and get comfortable.
More than ahlf of the fun ius in the shopping anyway!
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2010 Blue RT Audio & Convenience model Se-5 transmision. Dealer-added foglights, accent LEDs and extra speakers. Some RTS chrome windshield, front spoiler and top trunk trim, RTS frunklight and frunk liner, Top Trunk liner, Chrome lower air deflector, fendertip LED bulbs and ISCI floorboards added by yours truly...