I think Bally's score motor design is actually quite good. It is highly serviceable, and everything is generally accessible and easy to find.

The Gottlieb games, to echo what most others have said, are the best made. Great feeling games.

In the bingo world, there were two main manufacturers, Bally and United. The United games are a similar jump in quality 'feel' over the Bally games. I was very surprised to feel this difference when I picked up my (only, at the moment) United.

Any Gottlieb short-throw relay with the short switches is very difficult to adjust properly, and anyone that jumps into these games typically creates problems by adjusting a single switch and not verifying the position of every other switch on the relay. You don't really run into this with Bally or Williams. But, the short throw, when adjusted stays in adjustment well, doesn't attract as much dirt, and doesn't arc nearly as much when dirty (typically). 'Course, part of that's the 24V instead of 50V circuitry.

I really don't like a lot of the Williams units, but their score reels are pretty easy to work on. Bally's, more so.

Williams' score motor is a bit frustrating, though (to me). Lots of metal and very easy to accidentally snag a switch.

I think the Bally units are the best of them all. Their stepper design is very simple and serviceable. The nylon gears are easy to clean and the stepper itself is easy to adjust.

The Gottlieb score motors, as someone else said, have bad switches on the inside, but that's because everyone fixes those external switches and lets the rest rot. Once a Gottlieb unit is tuned, again echoing most others, it stays in adjustment for a very long time.

I've only worked on two Chicago Coin games, and each was a little quirky, but mostly Williams parts inside, so I can't really comment.

Genco and Exhibit games are also great! I like Exhibit a bit better (from a service perspective).

I really dislike working on a early-mid 70s Williams. The way they installed their relay banks under the playfield is often the perfect place for wires to get snagged and so forth. Not that I can talk much about that with Bally's shutter motor switches...

Heck yeah! Especially in the 60s - so pretty!

In the bingos, they can be pretty darn bad. The 'sockets' are just metal tines that stick out to push on the nipple with a little bit of surrounding metal to hold it in place/conduct. Those tines can get out of whack or cut into the bulb and cause flickering. This is the worst if you have a problematic socket behind a card on a Mystic Lines game - you've got to take off so many layers of stuff just to get to the socket. Luckily, you can normally fix just by pushing on the tine from the back, adjusting it forward a small amount, so that it cuts into the bulb better, thus continuing the cycle...

Their standard EM flipper sockets are nothing bad. I've also never had a problem with Bally's Jones Plugs, in any game, bingo or non, that I've serviced. Bally Jones Plugs, if exposed to a lot of heat, can warp, but same can be said of all of them. As long as you clean them (again, same for anybody), you're set.

I'm not as big of a fan of early Williams or United flat pack Jones Plugs, but those are kind of neat, too.

Bally's fuse blocks, on the other hand... I've certainly had lots of issue with.

For the most part, Bally's issues are very easy to correct. And one thing which I was alluding to above, they really, really thought about who and how these games would be serviced. Flipper or non, they tried to make it easy to keep the game earning. I think they did a very good job.