No one has mentioned the biggest advantage I have seen with the 904/A500: Lower first gear ratio. With street/stock rear ratios, that lower first gear will take you off the line much faster.
Rebuild a 904 with Kolene steels and Raybestos frictions or the equivilent and it will, IMHO, last just as long as a 727.
Volare cop cars with the 904 did just fine with many fleet operations (city of Aurora, CO for one) putting in shift kits to firm up the sloppy shifting and adding life to the transmission. If anyone can kill a transmission, cops can.
Craig