I have Thomastiks on it now, and I like them pretty well. When I bought it, the store had put D'Addario bass guitar strings on it, which was bizarre.
I haven't experimented a lot with upright strings - I started using Thomastiks 30 years ago on my Roth upright, liked them, and have stuck with them. I am sure there are lots out there that I would like as well or better but I'm a creature of habit.
Rick B.