While I do not have the 4-16, I do have both the 3-20 and the 5-25.
I think the glass in both is the same.....AWESOME. I have been shooting my 3-20 more in the last week, but that's just because I've been on a gas gun kick.
I like some things about the 3-20 better, but that's reticle and turret related, certainly not glass.
The glass between the two is equally incredible.