17J & 21J Movements

[eclipsewon]

It seems we are all fixated on eta and 7750 movements, as most chrono watches require those movement. I haven't seen many detailed remarks regarding 17J & 21J Japanese Movement.

As I browse our dealers' sites, I notice many watches with 17J & 21J, with and without "working power reserve". Now, I wouldn't be asking if I hadn't done an exhausted search on both sites, RWG and RepGeeek.

Many watches such as Glashutte, JAEGER LE COULTRE, Breguet, AUDEMARS PIGUET, etc., all have watches with the Jap/Asian movement, and without fully understanding if these movements are competent, it has prohibited me from purchasing them.

Does anyone have a reference web site detailing these movements? If The Zigmeister says two words, "Their Great!" that would work too.