How wide is a 2.2" MTB tire?
MTB tyre sizes are very variable, and the only way to be sure what size you will end up with is to read online reviews and/or see it mounted on a wheel in person.

mattnz is indeed correct in his comment that size can even vary between models from the same manufacturer.

The Conti Mountain King 2(and the XKing that shares the same carcass) in 2.2" flavour are well known to come up small and are generally considered to be a 2.0/2.1.  No need to be concerned though, as they are generally well thought of as XC tyres.

With these two tyres i'd be more concerned about getting the correct rubber variant of rubber compound (either the PureGrip or BlackChilli) than the true size of the tyre.