LOL its turned in to an argument!!
I own an M-jet so i am biased but if you want the power and the MPG get an m-jet.
If you want a bit quiker off the line speed get the t-jet.
Plus points of both cars:
M-jet has better mpg, in gear acceleration (60-100 quicker), more refined,
T-jet sound better, 0-60 is quicker
Minus points
M-jet sounds like a tractor
t-jet eats fuel.
Another good thing about the m-jet i find is the fact you can smash boy racers to bits and rub it in their face by filling their face with black smoke!