I have a 21 and 30 and the 30 fits my hand perfectly.
At SHOT Show 2012 a little while back we got a brief look at the Gen 4 version of the Glock 21. Fortunately for me, I had just purchased a new Gen 4 G21 just a few days prior to the show, and we can now get a chance to look at it from a more “hands on” point of view.
Once I pulled the G21 from the Glock box, I noticed some differences right away from my earlier Gen 3 guns. First off, the grip has the characteristic nibs that Glock calls “polymids” set in the familiar RTF, or “Rough Textured Finish” pattern. Actually feeling the Gen 4 version of RTF, and carrying it for a bit, I prefer it over the Gen 3 RTF2 style. The RTF2 surface was a bit more aggressive than I cared for, and was rough on clothing. As a big fan of the Glock overall, this was a welcome change, because to me it feels “just right” and I think I grip it more securely than the Gen 3.