Cool, I'm curious too.
FWIW, from a physics standpoint, vacuum pressure can never exceed -14.9 psi.
Kink resistance, durability, oil resistance, crush resistance, and minimum bend radius are also all important concerns.
Something else I like about the 1-1/8" hose is that it comes off the barb really easily when you loosen the hose clamps. I don't have any quick release fittings in my system, so to pull a sack out I have to undo 3 hose clamps.