Why not try both, some in pots, some outside in your nursery bed.

If you are talking about Verbena hastata Blue Spires, its supposed to be hardy, but I'd be inclined to pot them up and keep them somewhere like a cold frame or cool greenhouse over winter.
I ask about the plant because I see it says above "on plant Verbena hastata" but there are several other plants also with the name "Blue Spires" - Rosemary, Perovskia and also Salvia.