I would say it depends on if the game has decals or not and if there is already existing damage you are looking to cover up.

If it has decals the small metal protectors that mount to the cabinet under the legs seem to be the way to go. Silk screened and painted cabinets seem fine with the PinCab Protectors, but if there is no damage to cover up on them....you might as well go with the metal plates with them also.

I've used the felt ones, there thick and very good. I stay away from plastic as over time they tend to stick and can rip the artwork

I have an issue grasping how the metal ones would work. I mean, isn't the metal going to dig into the cabinet just like the legs would?

The felt ones make the most sense to me, but I've only used the pincab plastic ones.

Metal ones are much smaller than the legs, making them invisible once installed. It looks like the legs are hovering off the cabinet by the thickness of the metal protector hidden underneath.

The metal protectors are designed to be secured to the cabinet by two (2) screws, so they should not move around at all and should not dig in. Of course, you have to have the guts to screw them to the cabinet (LOL), but this is all hidden beneath the legs, so I've not minded doing so.

I haven't screwed mine to the cabinet and haven't had any issues. They really don't have any room to move around once installed unlike pincabs that have play to move up and down and cause wrinkling. The screws are nice and I can see why Stern uses them so they come already installed, but if installing afterwards I don't see the need for the screws and I haven't had any issues yet not using them on my machines without them.