I work with a local pinball bar that's been around for a long time. Since the 90's we've been buying new machines, running them there until they die and then I haul them off and restore them.
When we were buying Bally/Williams, we'd have them shipped direct to the bar, unboxed and put on the floor for immediate use. We do not do that with Stern pins. I have to have them shipped to my shop, setup, FIXED/tweaked or flat out repaired before they can go on location.
With B/W pins, we got huge lifespans out of them. AFM lasted 15 years, got the hell played out of it and was still mostly functional when we pulled it out. Monster Bash lasted almost that long, TOM, etc, all had really long runs, taking in plenty of coin.
With the latest version of Stern (2000 on), they have improved drastically over how bad they were in 2001-2003, but they still don't last worth a damn. If we can get 4 or 5 years out of a Stern in that same exact location, we feel lucky.
Stern's roller switches instead of optos in troughs, LOTR's sword lock, etc are crap. Brand new they work fine but they don't hold up like an opto version. Almost every single Stern that doesn't have the armor around the flipper buttons is worn through to the wood on their crappy cabinet art. (That was okay when they included the side armor, but now it's mostly just an option)
Stern's choice to use one triac instead of the three stage system that B/W used leads to more frequent and quite a bit more expensive repairs from blown power driver lines. (Yay for $7+ transistors dieing)
If you compare the two, there's no reasonable doubt that Sterns since 2001 aren't built anywhere near as well as Bally/Williams were.