There are differences but after you do a few it's not that significant. You may develop preferences on how certain components are designed, but if you've done four games already you won't have much trouble. EM repair transfers fairly easily across manufacturers.

You'll find more significant difference between the vintage of EMs. Those made
in the 1940's use different parts and they are not always of the same quality
as those used in 1970's EMs. The biggest difference in operation is Genco who
did not use score motor assy's early on.

Once you get into bingos, prepare to get your mind blown! Their complexity
and how they work is at another level.

My first six games were Williams. I heavily relied on the schematics and manual to get them working properly. I actually surprised myself when I started buying Gottlieb machines. I was able to troubleshoot them and get them going before I got the schematics. The only thing I am not a fan of on Gottleib EM’s is taking apart and cleaning the score reels. I find the Williams much easier.

You should get Henk de Jager's book on EM repair. He treats each manufacturer's methods and designs as a "system" to be learned, parallel to SAM/Spike/etc. in the modern-day pinballs.

IMHO, Williams EM games had the best documentation, so it will be an effort to learn the Bally or Gottlieb system and how to discern the info that Williams just provides in print. In particular, Gottlieb allowed multi-purposing some relays without explaining them in the manual. Luckily, on-line resources have filled in a lot of the knowledge that Gottlieb failed to deliver.
.................David Marston

There are subtle differences but of course the basics are the same. The orientation of mechs and general build of Ballys will remind you most of the Williams games. Gottlieb differences will stand out but you'll adapt without too much trouble.

In my opinion Williams games are easiest to work with, usually easy to get to everything, the relays are super easy to clean and identify switch gaps. Bally's are my least favorite to work on because the logic always just seems weird and there's always a bunch of relays in the back of the cabinet you can't get to easily (always the ones you need to get to of course).

Gottliebs are a bit of a pain the ass, always having to remove pins to get to the relays properly, and those relay reset banks that are virtually impossible to accurately clean and gap without taking the whole unit out and turning upside down. Their latch trip relays are also a legendary pain in the ass with their tiny travels and seeming allergy to staying in proper adjustment. And of course their horizontal score motors were also designed to annoy and piss off techs.

Still I'd probably put Gottlieb at number 2 in the "which I'd prefer to work on" behind Williams and ahead of Bally.

I find vertical-cam score motors (Williams and Bally) more intuitive, but more difficult to adjust the packed-in switches on, than horizontal cam score motors (Gottlieb and Chicago Coin).

One needs to make a short nose switch adjuster.

My first to EMs were Gottliebs, then I got a Chicago Coin which seemed a little intimidating. I think the documentation was more different / strange than the actual components or circuitry. In a perfect world (i.e. bigger basement) I'd have a few of each manufacturer. I love seeing how different manufacturers did things uniquely (or not).

I've been able to play Flip-Flop at a local club and it's a fun machine - I imagine the flip-flop mechanism are pretty interesting / novel.

In my experience in owning all of them Gottlieb has the most quirks and Williams easiest to work on.

The Gottlieb vertical switch motor never gave me any particular problem, short relay arms, AS ratcheting relay and relay banks as always fussy though. On some of the mechs, Gottlieb likes to put a lock nut which you will shear the fastener off if unaware.

Gottlieb has a reputation of being built like a tank that is not really true. They are well built but my experience is they are much harder to keep dialed in than a Bally or Williams.

CCM is junk.

Depends on the vintage; I have a 1969 Moon Shot that is an utter tank. I had a '74 Hi Flyer that was good but you could see the cost cutting was starting to happen.

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For me Gottlieb relays and decagon units stay working fine for years and years IF you adjusted and cleaned them right in the first place. They are much easier to screw up if you just start fiddling with them not really knowing what you're doing than Bally or Williams which are more foolproof.
Williams and Bally score reels are looser and floppier with digits more likely to be slightly out of alignment on the backglass but they are more reliable under heavy use. I do like decagons but to me they are kind of overbuilt and very tightly toleranced compared to their other units.

You hardly ever see anybody mention Chicago Coin when comparing EM manufacturers. Anybody in disagreement that they were cheaper, clunkier and absolutely less tank-like than the Big Three?

Agree wholeheartedly with this statement.

I’ve been repairing EM’s for close to 40 years, I quit working on Chicago Coin 1970’s era games more than 15 years ago due to their score reel design. I like their Hollywood/Cinema game, but getting them to reset to zero and score 500 points properly at the same time is darn near impossible.

I am working on a 1972 Casino and what I have found is that it has a lot of
little things that cost money...
For instance, all switches and lamps are fastened with solder lugs.
or the custom pop bumper wafers.
Overall, I realized that CDI splited up a lot of circuitries that other manufactures
would have simply simplified.
I agree with you gdonovan with the game Hi Flyer, Chicago Coin was getting pinched.
and also FrankJ with the score drum units.
CDI designed drum units left off the stop tabs... so the numbers always look wonky, and
never cleanly aligned .

I had to go through a Blue Max and get it running, It didn’t really seem that bad. Once I got it working it stayed working.

The biggest issue was lack of availability of coil stops for the score reels.

I had a machinist make me a stop.
I used the Gottlieb coil stop that Pinball Resource has...
The guy recute the bottom stop to act like a CDI stop...
I was able to fix the heavily exercised 00-90 unit.

CCM made a lot of arcade games. They never seriously challenged in the pinball world.

To me their games were cheap and short on features.

I don't know that decagons are over built. What they are is overly complicated and fiddly. I used to hate rat traps but if you can work on them out of the game they're easier than decagons. Just get those switches adjusted before the circuit board goes in. If not you're screwed.