Quick question - Does it take more resources for you to run 3 cards separately or together?
Also, I would have to say that part of this depends on each payment's pool reward method and fees.

If you've already accounted for these considerations, the question is analogous to betting strategy in a lottery: Do I bet on 3 numbers for $1 apiece or do I bet on 1 number for $3?

Due to the stochastic nature of Bitcoin mining, no one strategy will be predictably better.

This is just my newb opinion. Other thoughts are welcome.