I've never found Gottliebs any better built than either Williams or Bally. I've generally found Bally and Williams easier to maintain, especially the later EMs when Gottlieb went to some of their follies (Ax relays replacing trip banks, AS steppers, etc). That's not to say Williams did it all right, their match units later in the game are no fun either, but in general Bally and Williams are easier to dial in and keep dialed in. Gottliebs, with the short throw relays, can be a bit fussy at times. And there's simply no comparison when we're talking 70s Bally/Williams score reels vs the farce known as the decagon. The best comparison I can come up with there is German vs. Japanese cars. Japanese, simple and reliable. German, wonderful piece of engineering, overly complex in design, more prone to issues.
The wedgehead design is wonderful to look at, but in some ways the Bally/Williams lift out backglasses made working on the head easier than the tilt back design of the wedgeheads.
Bottom line, though, is they all made some fun games, all made a few duds. In general, Gottlieb made fewer duds, while especially in the mid 70s, Bally/Williams lost their way for a bit.