Depends ...
At various times I likely would've given different answers.
Sometimes I would've answered that a medium-bore .357 Magnum/.38Spl was the ideal choice for my needs ... and at other times it would've been a .44 Magnum/Special ... with my choices including both DA & SA revolvers at different times.
My original 3-screw Ruger Blackhawk 4 5/8" .357 Magnum Convertible, with the factory fitted 9mm cylinder, would certainly offer some ammunition options.
My 4 5/8" Blackhawk Convertible, with both .45 Colt & .45 ACP cylinders, would make a decent choice, too, I imagine.
While I have a very strong preference for the versatility of the .44 Magnum/Special combination, I'd likely eventually have to say that a nicely done medium-size DA revolver chambered in .357 Magnum would probably be my choice in the final analysis. As much as I prefer the SA revolver, there's something to be said for the attributes of the simpler-to-operate trigger-cocking revolver in many circumstances.
It's only a medium-bore, granted, but the ammunition variability, especially nowadays, is an advantage that's hard to dismiss, all things considered ...
Make & model?
Having owned and carried a fair number of Ruger Security/Service/Speed-Sixes, and other Ruger DA/DAO revolvers, and having previously been issued a M66 & M686 for my LE job, I'd probably go for one of the GP-100 models for long-term durability ... although I still kick myself for not picking up a Redhawk chambered in .357 Magnum way back when.