If I were using a dual fan setup, I would want them to come on in stages, one first, then the other if needed. If they need to both be on at the same time, at least have one delayed a second or two, that would lessen the current spike on startup. I do like a manual switch as well, just in case all else fails and you need it on!
Usually you have them come on at different temperatures. So say one comes on at 170, the other at 210.
