[blau911]

I have had them both and I must say that my 73.5T CIS ran great. I didn't think I would like it after hearing how other people disparaged it. But the CIS ran like a clock, never stuttered, popped or felt sluggish. It also got great gas mileage as Techweenie above already mentioned. Lastly, it pulled better than any 911T I have ever driven (I have driven maybe 12-15 911T's over the past 10 years). It had really nice smooth acceleration, with really nice power between 3000-5000 rpm's.
The other big advantage of having an 73.5 CIS car is that when the engine finally does die, it is REALLY easy to swap it out for a 3.0 SC motor (early 911S hp and lots of low end 91T torque) without any wiring issues.
Anyone who has owned and/or driven many early 911's, and has also owned a 73.5 CIS will tell you that the CIS is a superior fuel delivery system. It is also one of the nicest driving early 911 cars ever built.
Don't let others kid you about its shortcomings. There are none. If your car is rust free and in good shape, your 73.5CIS will command good money if you sell.