If you want games on route to earn then both or whatever earns the best for initial purchase. For working on them like moving and set-up the Stern / Data East one bolt back box is hard to beat. The SAM board set is also great for ROM updates and none of mine have crapped out. The Bally / Williams games still have a different flipper feel but the latest Sterns are pretty damn good IMHO.

Williams coil stops and bushings are cheaper but I have replaced very few Stern parts.

A side note getting a NIB game back in the Williams heyday you had to have a connection with Betson or someone connected to "get" you a game. I saw very few if any NIB games being dragged to anyone's house. The closest I came to a NIB game was at an Aladdin's Castle arcade when they got a brand new TOM in and I waited for them to set it up and be the 1st one to play it. It was the only new Bally / Williams game I have ever played.

Stern games on the other hand are available from multiple sources and I have purchased 2 NIB Sterns thus far and a TSPP that had 93 plays on it just out of the box. Stern makes a solid game.