i had a similar consideration when i bought my 17. the 21SF was calling my name too.I had been pretty set on getting a glock 17 but now I am wondering if I should get the 21. Is there any real difference besides the caliber and the width?
all it came down to for me was the grip, the 17 was just *right* for me
caliber was not a consideration because 9mm and .45 are my favorites to shoot because of their smooth recoil characteristics. i honestly think i would've been just as happy with the 21sf though to tell you the truth, haha