You can get a trial account from the warcraft homepage.
I believe that can only go to 10th or 20th or so, and has a few limitations as well.
Regardless, you can see how each of the computers handles a copy of warcraft.

I'm not sure how they would do.
But testing will be a good way to find out.
Go somewhere like Stormwind or Orgrimmar which has a bunch of characters in one area.
That's probably a good stress test for each system.