Mint is for people who just want stuff to work and not fiddle about too much. It does that very well. Anyone who simply wants an alternative to Windows that is easy to get into and use will be perfectly happy with it. If you want to customise everything to a t, Mint isn’t for you
Arch is bleeding edge and frequently has minor bugs as a result. This is probably fine for power users and people who want to learn Linux but I wouldn’t give an Arch distro to someone who isn’t techy. They also likely won’t appreciate the frequent updates to applications that they depend on to actually do work.
(I used Arch for almost five years and think it’s one of the best distros)