It depends on if you looking for a removable top or a coupe. If you are looking for a removable top, then '97 and up are the way to go. '95 and '96 have removable tops, but they have the 3.0L engine with the 5 speed. '97 is when Acura changed to the 3.2L and 6 speed transmission, increasing the acceleration time a bit to make up for the difference in the added weight.
Personally, I went with the '94 as I do not like convertibles. There are coupes ('97 - '2001) with the 3.2L and 6 speed engine out there, but you have to look very hard as they were special order only - thus pretty rare. The Zanardi edition is also out there ('99 with 3.2L and 6 speed), but only 50 were made.