If you cant find one then get the 21J.
For me, I dont like faux chronographs. I like the chrono's to work. If Im going to get an automatic watch with chronograph subdials, I like for them to work.
21J is generally more reliable in the sense that you will have fewer problems with the mechanics of a bike than you would a car. Sure, the bike wont break down, but there are some differences.
If you are talking about a simple 3 hand watch like some of the panerais that use 7750's, the higher beat rate is generally what is being sought by using a 7750. I can understand not wanting to pay the premium on a 3 hand watch, but the watches themselves are usually higher quality.