16mm performance ?

shaki, the 20-50mm is really surprisingly small. don't get the wrong idea that just because it's a zoom that it is big and will take some significant space and it only zooms in and out to a roughly half a cm at full extension at 50mm.  so don't worry about it too much.

the reason why I'm recommending you the 20-50 is not because it's a zoom, but because it's noticeably better than the 20mm in overall IQ performance. it wouldn't make sense getting the 20mm prime unless this lens size comparison still makes a world of difference to you.