Good question, but I think you're going to get a bunch of varied responses from people who've been exposed to only some of the many great machines out there (myself included). In general, the more complex a machine is, with more toys, flippers, ramps, etc on the playfield, the more problems and breakage usually occur. These are mostly newer games. I've seen some MMs that always have a broken plastic or two, and simpler, older games like Skateball and Blackhole that have only ever needed coils replaced.
Bally/WMS seem to have the best playfields. Even compared to new Sterns, the Bally/WMS playfields from the mid-late 90s generally show little wear- something in the sealing I bet, but there's generally not nearly the level of cracking or dimpling that you see in Gottliebs or Sterns.
Roadshow and Cactus Canyon seem to be perpetually breaking their complex toys. Who Dunnit's ramps (elevator), stand-up targets and roulette wheel are all frequent target of abuse also, that have lowered game quality and price. And while I love Haunted House's design, parts of the lower playfield seem to stop working.