If you declare a MAYDAY, I'm going to Squawk you 7700 and send you direct to where ever is the most expeditious fix and then coordinate. If you declare a PAN, I'll consider 7700, coordinate first, and then I'll send you direct on the most expeditious route once it has been all tied up which could take a few minutes. I also agree with Gonzo, there is an element of what you tell us in what we do next too, and as has happened recently with two MAYDAYs and two PANs all heading for the same piece of concrete, if you only declare a PAN you could get "take up the hold for one spin, MAYDAY traffic ahead", it's rare, but it's happened!!