I see the Shield mags as a this or that thing, not both.

The steel Shield chews up the Glock mag catch. The steel Shield mag catch chews up the factory Glock mags... According to many reports. I'm not willing the spend a few hundred to find out.

My 48 carries & works nicely the way it is. If I see a potential need for 15 or more rounds, I move to a 17 or 34 with the big plus 2 mag for 19 rounds.