App titles. You can have less margin on the edge since you don't have to considers the app title length from the other side.
I guess, this would be pointless:
36+38+36+38+36 (18+19+18+19+18)
since the 2nd and 3rd icon wouldn't get the benefit of the extra spacing.
So the reasonable option would be: 34+38+40+38+34 (17+19+20+19+17)