AC/DC has a proven layout, but feels too similar to many other games. Great rules and sound. A real eyesore to look at. Premium/LE is the only way to go. Pro feels too barren without the proper bell swinging and mini-playfield.
Avengers' layout is unique, spinning toy can't be found on too many games, Hulk bash toy w/ magnet is great. The cab is pretty ugly on both LEs imo, but a lot of people like the Hulk for some reason. The added ramp, drop targets and lifting ramp don't justify $2000 more than the pro in my book. LE/Premium is also much easier because the drop targets on Thor slow the ball way down and make it easier to control shooting him, in addition to the left flipper being fed from the added ramp from a easy shot (Hawkeye), as opposed to only being fed from a very difficult shot on the Pro (Black Widow). Entirely a mode based game, won't score or do well without entering them.
My AC/DC pro didn't last here for more than a few months and I never see myself getting another one (Pro or Premium). My Avengers Pro has been here much longer and barring a good trade deal on it, I don't see it moving. If it did leave, it would be replaced eventually with another pro unless I found a Premium/blue LE at a very cheap price ($5K).
I'd choose Avengers LE over AC/DC LE, but I'm probably in the minority on that one. Would choose Avengers Pro and another $2000 pin instead of the Avengers LE. Probably a T2, since it has a near-identical layout and main toy (cannon).