As far as outlets, they’re all about the same in both looks and features . The Leviton, GE, and enerwave are all on the official “works with SmartThings” list.
But any certified Z wave outlet should work fine, including Cooper, go control, evolve, etc.
Leviton announced a Z wave plus model early this year but they haven’t brought it to market yet. I’m sure there will be some out from several brands by March, but Nothing specific yet.
As far as the plug-ins, which we usually refer to as “pocket sockets” just to make it clear which device class were talking about, there’s a lot more variation with those in style and features. The following thread has a good discussion: