One turntable with two arms, or two turntables with one each - which would you prefer?

Which would you prefer, if budget allowed: one turntable with two tonearms or two turntables with one each? What would your decision criteria be?

And the corollary: one phono preamp with multiple inputs or two phono preamps?

Assume a fixed budget, but for the purposes of this question, the budget is up to the responder. Admittedly for this type of setup, there will be a sizeable investment once all components of the chain are factored in.

I'm curious to hear how people would decide for themselves the answer to this question. Or maybe you've already made this decision - what do you like about your decision or what would you differently next time?

Cheers.