Overall I've had good luck with Spike games and they've been pretty reliable. Below is what I've personally operated or what I've regularly serviced that was on location. I've also noted the board related issues I've had by platform with the number of games operated in parenthesis.
DE (2)
- 74HCT154 replaced (22 year old game at the time)
- Proactively replaced the 100uF caps on the power supplies
Whitestar (4)
- No board issues
SAM (10)
- No board issues
- Service bulletin exchange for the magnet board on Metallica Premium
Spike (8)
- SD card bad (technically not a board issue, but an issue inherent to Spike)
- No backbox sound, amp failed, warranty return CPU board for replacement
- Flaky node board 8, unresolved. Appears to be connector related, probably because the board is so close to the left flipper.
- Service bulletin to add caps on Spike 1 game node boards
- Service bulletin to secure node board diodes on Spike 1/2 games
So in this small comparison, I've had more issues with Spike than the other platforms. Not many, and you probably can't really draw any great conclusions. But when you throw in the lack of schematics on Spike, the difficulty of servicing Spike boards, and the lack of compatibility with Spike, I don't feel as good about it as DE, Whitestar, and SAM. So in my experience, although the DE, Whitestar, and SAM games are much older than the Spike games, they have been just as reliable if not more reliable.