We did Greater Miami & Naples for a workation last winter - unfortunately during a cold week.
IMHO . . . . SoBe is nice to visit but I wouldn't want to stay there unless you count yourself as one of the 'pretty people'. In January, only the tourists brave the beach. Some good restaurants & glittery (and expensive) hotels.
I did find an interesting place to stay in South Miami - Coconut Grove specifically - at the Grove Isle Hotel. Decent digs & not obscene prices - a nice quiet oasis on a private island (with a bunch of condos). Give the restaurant a pass except for breakfast but there are lots of options a taxi ride away.
From the plane:
It's the low building in front of the 3 condos.
Ian