For out mapping missions we fly both P4s and P3s but found that the P4 consistently had a longer life - landed with more battery left. In worse conditions (wind) the P4 did relatively better, so much that we had to tone down the missions so that the P3s could be guaranteed to complete.
And that is with the original P4 batteries not the new bigger ones. So it comes down to what you value more, your time (get the P4, maybe with the new batteries) or your money (buy P3As and put up with more missions to cover the same area or P3Ps if you require 4k).