I find SS a lot easier to work with and troubleshoot. Pretty much everything is based upon on/off logic and mostly direct inputs/outputs.

With EMs, I find following the mechanical, conditional, and chain logic a little difficult. So not only are you dealing with just the operational logic, but also physical problems with the mechanisms that might or might not be obvious enough to track down. Then on top of that, some the wiring can only be identified based on color, rather than pin positions. With games that are decades old, the wire colors are not always easy to determine, and that adds yet another layer of complexity.

I can certainly appreciate the ingenuity it took to design EM games, but I find SS games much easier to work on.