RX-7 looks....just wow..Mk4 is awesome too, but FD has its own thing going on there...also, FD is a "sports car" and the Supra is a "grand tourer". All FDs are TT, whereas about 1/2 Mk4s are TT. FDs are much lighter, Supras are "more reliable" and probably a bit safer too. Both have incredibly smooth engines, but I think nothing is smoother than a rotory

However, when it comes down to it, FDs cost less than half (most of the time). The rest of the money could go towards mods, reliability, whatever. Just your preference really.