What a thread!

Sidecut for sure. Manbun is more of a fashionable hipster thing, whereas Jon would always opt for a mainstream alternative (see his 80s hair). Bieber is/was rocking a sidecut and he's pretty much the Jon of 2010s.

Anyway, I'm glad he didn't start today because he is still yummy (like a fine wine the man gets better with age, am I right ladies?)