It has been posted before that the 4r calibers are little more decorated than 7sxxb calibers. There might be some other small differences, but they are not many. Both are comparable.
Not all around, only in the rotor and the part of the back plate visible through a display back. the rest is still stamped and unfinished, and AFAIK, for the most part stock 7s. I'll give you the mainspring material though.minidriver said:4r15 and 4r16 are better finished movements all around and they use Spron 510 mainspring that extends the power reserve to 50+ hours.