I attended both shows last year (including volunteering time for 5 days @ MPE).
MPE definitely had more machines and a lot more people. expect to stand in lines up to 5-6 people deep on saturday and sunday. not too many vendors for parts (last year had gary from IPC setting up late (and almost not getting display space due to miscommunications) and 2 other smaller vendors with boards, key chain fobs and the regular assortment of leg bolts, levelers and other such staple parts
PatZ was a much more relaxed (and spread out) environment to the point that it looked almost empty, however it wasn't for the lack of games, just a larger room. power was definitely an issue (and it will interesting to see if the load balancing issues have been addressed). plenty of vendors, including coin taker, IPC and a few others (that I can't remember off of the top of my head) and mr. pop (a gourmet pop vendor), mix and match for some great flavors including 'dang! that's good' butterscotch rootbeer.
python anghelo made the trip to both shows last year and was an absolute joy to chat with.
python, jack guarnieri, and steve richie all participated in conferences at the fire side area @ MPE and for the 2nd year in a row, a NIB jersey jack pinball machine was awarded via a raffle for those that brought at least one machine or volunteered time (and participated in the saturday morning 'pin brawl' tourney)
both shows have plenty to offer but are two entirely different animals. like many have claimed before, if MPE grows any more, they definitely need to look for a different venue that offers more space.