That could be the difference between two rooms, the Mac room has carpeting and drapes and heavy furniture and the Windows room has wood floors and bare walls.
That could be the windows machine with voice processing.
When you do direct comparisons like that, it should be the same person saying the same words in the same room. No I don’t think buying a Mac is going to help.
I posted in the instructions for a voice test not to say “one, two, one two.” Go down the link for “Speak or Announce.”
If you’re trying to record for ACX like your other post implies, you really don’t want to record in different rooms. You want to record, from start to finish, in the same spot, with the same settings. If you switch things up, you’ll pass the automatic checks for files, but when you have human QA listen to it, they may turn you down because the noise from one room to the other may be too distracting to them.