This to me is one of the mistakes people make with multiple monitors. IMO to get the best benefit, the 2nd monitor is for utilities, mixers, plug-ins, manuals etc… Keep the project window completely on the main monitor. By keeping the project clutter on a different screen, it will increase your speed.
However, if I had to make my choice between 2 22’s and a single 30"… I’d take the 30.