The down side of the FT2 is that one must do the Nikon shuffle every time a lens is mounted. The FT3 frees one from doing this quick dance. In general, this is the major benefit of the Nikon AI system - quick, easy, and fool proof lens mounting.
Definitely a waste of 2 seconds.
All kidding aside, I prefer the automatic indexing system, it's just nice to have a camera than can open aperture meter with old and 'new' lenses, when I already have other Nikon cameras that have auto indexing.
I picked the FT2 over the FT3 because it had that, and over the older ones because it had improved features (focusing screen, modern battery etc). A 'regular' Nikon like an FM is an easier shooter, with a more sensitive and useful light meter.
When you use a camera with a modern light meter, it is a bit jarring seeing the Nikkormat's needle pop to the top of the scale because the light levels have exceeded its performance envelope.