which one would it be?
When is your visit?
Wineries are relatively small and a lot of private ones....not really the same format as US wine tours/ commercial wine tours that is .
Valtice would also be a consideration.
That's the one I mapped out.
You should still visit Mikulov the town itself if you have time. The views from the castle walls are nice...looking towards Austria
If you are doing public travel, taxi ride between the two is affordable. As well, the ride from Valtice to Led nice ( part of UNESCO)