The Rainier Arms Magazine Advanced Release System (MARS) provides shooters of Glock Gen 1, 2 and 3 pistols an aluminum release that enhances speed reloads for both left- and right-handed operation.

From Generation 1 to Generation 3 (1982 - 2009) The first Glock pistols, ... Although Gen3 magazines can be used with a factory configured Gen4 magazine release, ... Winchester .21 Sharp.

So Gen 4 wins here, no doubt. Gen 3 Glock 19s having a smaller low-profile magazine release button wouldn’t be an issue if the user practices pushing it enough times, but the larger magazine ...