Its not a matter of whats stronger, its a matter of whats better supported by the aftermarket. TH400 is like the 9" rear, there are tons of stuff availible , from case to gear sets. When i switched to a t400 the converter was literally 400.00 cheaper. Seriously i priced the same converter for a t400 and a 727,
Best move i ever made becasue there is so many parts availible and the technology of so many people using a t400 now trickles down

I know I know its hard for people to accept but who cares whats stronger, i care about what WORKS the best