People are loyal to what they put on their car (brand wise) so it is hard to get someone to be "objective" about which set-up is better. I think they are both great systems from great companies.
That said I have a Heffner TT that has been nothing but a pleasure. 1019 rwhp on race gas, about 875 on my 91 tune I drive around town. I did 22 runs over 200mph at the last mile event I did and drove the car over 300 miles round trip to and from the event. I have put about 2,500 miles on my TT with no issues. My only complaint is I wish I would have done it sooner.
I think more people would go TT or TT/SC if the cost wasn't so high and there were more out there for people to experience. It is well worth the cost, but I have to admit I was a little nervous changing my car that dramatically without ever having driven or been in one. If you can even get a ride in one I would highly recommend it. I gave a ride once to a very experienced race/stunt driver and he said he never felt acceleration like that.....and I was only running my 91 tune. Another Forum owner in a stock GT was behind us and said he has never seen a car pull away from him so fast. :thumbsup :banana
One other important note. I drive my car....a little less than 12k so far, and the TT did not affect the drivability of local cruising. It is great in every type of driving. :cheers