Tough call. I own both, and would have a hard time parting with either of them. I'll try to break it down:
- - - Wh20 just has a certain "charm", the original art, the music, callouts, colors, shots... it's just an all around great game. I consider it my favorite of all time, and I doubt it will ever leave.
Still, I've seen people absolutely crush the game (ralphwiggum). That makes me wonder about longevity for players that are better than myself. I don't think spamming the center shot is necessary for a great score, but there are times in gameplay when you'll find yourself aiming for that shot several times in succession. I think that's one of it's knocks.
It's got one of my favorite MBs in all of pinball (and one of the best MB starts). The triple jackpot is insanely satisfying, as is stacking 5x with MB or bigfoot hotfoot. There's a good variety of shots, the playfield layout is one of my favorites, ever.
Again, I think the downfall is that better players with great ball control can really exploit things, especially the MBs. Since you really don't need to make any shots that would put the ball out of control during MB, good players can keep this going for quite a long time.
The sound quality is also not very good. I guess it doesn't really bother me, personally - I love those midi style sounds, it remind me of SNES and the like. Still, I've seen others express concern over sound quality, even after speaker replacement due to it being mono sound (can't remember, exactly).
- - - AC/DC Premium has a ton of different strategies. Sometimes that will actually prevent me from playing it. Sometimes I don't really want to "think" through a game. At it's core, it's really a simple fan layout game with a great ruleset. The color changing inserts look really cool, AND they're functional. You notice it in modes like Thunderstruck (one of my favorites), all the shots that will give you points will be flashing blue, but the most lucrative shot will be flashing white. That really helps to identify what's what in the confusion of a MB.
The risk/reward on this game, as I'm sure we've all heard a million times, is really unmatched. Do you cash in your 30m Song Jackpot? Do you try to get 2x or 3x going first? Should you try to start a MB to build it further, and possibly collect it's equivalent Song Bonus?? Getting a huge Song Jackpot is one of the best feelings I've had in pinball. Losing a large bonus is devastating, especially when it's due to your own greed.
One of the issues with the Premium is either ramp will load the cannon for the Song Jackpot. It can be frustrating to avoid both ramps when you want to save that shot. Keep in mind, loading that cannon means you either collect the jackpot, or it will continue to build. The problem with the latter, is that you will need to relight the cannon, that's done by lighting "fire" 3 times. I know you can disable either diverter, but that would really seem to mess with the balance (since then, the same ramp would load the cannon, and start MB).
The theme is really well integrated. The game really gets rocking during MB, the guitar riffs to signify jackpots is really well done. Also, the ability to swap out songs is great (even though that's not really a game feature, more of a benefit of pinball's very talented modding community).
The sound quality is great. Get an external amp for it, and it sounds amazing.
The lower PF is fine. It's not special, and it's not exactly fun. Getting some consecutive loops going can be slightly satisfying. Overall, I seem to avoid modes where the lower PF is active, unless it's competitive play.
Everyone loves the bell. I do too! There are some things that bother me, however. You hit the bell and it swings. Awesome. Except another shot to the bell within a few seconds afterwards probably isn't going to register. Even when the bell is almost done swinging, it's not a sure thing that your shot will count. This bell IS controlled (you can hit the VIP pass and make it swing, for example), so I'm sure a code update could reconcile this. If you make it PAST the bell into the scoop in anything other than Hell's Bells (one of the hardest shots in the game), you get nothing, it just kicks the ball out.
I know it's not popular to say anything negative about AC/DC. It is a great game as it stands, but I wouldn't call it "complete", I'm sure it's current code is not Lyman's final vision.
- - - Bottom line - I love both of these games, they're both Top 5 for me, personally. I tried to give my thoughts on each (both positive and negative), please feel free to ignore everything I said!