System 11 games have a handful of known flaws that need to be addressed and bulletproofed. Troubleshooting info on System 11 games is readily available for the most part.

System 80 games have a handful of known problem areas as well, but this system is incredibly well documented. I wouldn't listen too much to folks trying to dissuade you from them if you want to own one.

System 3 games are built like tanks, and rarely have major issues. There are a few documented problems, but most are easy to address. Unfortunately, board-level troubleshooting & repair info for this system is pretty much non-existent. Repairs to the driver board can be done using your experience with other game systems based on general concepts on how driver boards work along with the schematics, but other than that--non-booting boards are difficult to troubleshoot on your own. But, little documentation for the boards also means there's rarely issues with them that *need* to be documented.

This is true--Gottlieb games have their own gameplay style and aren't always as deep as some cherished classic sys11 or WPC counterparts. There are a few desirable system 3 titles, but also a fair number of duds. But, not every Williams title was a big hit either.

On the other hand, if you want to find a DMD game for under $1k, there's a few Gottlieb titles that still can be acquired for that price.