Not sure what you mean by selectable, but they sound like the same thing to me. GMs systems have been part time 4x4 for years. The last years to have it was when they still had solid axles and used full time drive slugs and a full time tcase (similar to an NP203). Since then GMs are very similar to Ford in that you have a selectable (part time) transfer case. You can select 4hi, 4lo, or 2hi (neutral if you have a manual tcase). The biggest difference in recent years between the 2 has been the actuation of the system. Ford uses vacuum actuation and in the mid/late 90s GM used the imfamous wire setup
I think now that they have dropped that and have gone vacuum. So for the most part they're the same system anymore.
Linear Mode
