I just installed a Robbins vinyl top on my TR4A, and I find it completely adequate. It seems to be of good quality, and I suspect it will last longer than I keep the car.
Back in the 1960s, the rear window of my TR4A top turned yellow in a couple years, and I replaced it soon after. If the window material is still that bad, I see no point in spending more for the top. However, I think it's likely that the quality of the material has improved in the last half century or so.