I don't really believe that slower drives = more endurance.

It all depends on:

a) NAND quality and drive size.
b) How gently the controller programs and erases the NAND, to improve NAND life.
c) How the controller detects and handles blocks that wear more then others, while not going crazy due to the average wear increasing.

There have been slow drives that die early .... like the Patriot Torqx 2.
There have been fast drives that last a long time .... like the Samsung 830 is proving to.