Monos Carry-On Pro vs Carry-On Plus: Airline compliance, real-world experiences?

Debating between the Carry-on Plus and the Carry-on Pro model - the Plus is a bit larger and the pro is quite a bit smaller. Just worried about it being ok to be used as a carry on for most airlines. 

Classic Pro - 22 x 14 x 9"

Classic Plus - 23 x 15 x 9.5"