As for ACDC Pro and ACDC Premium...they are only the same game in some ways, but play significantly different, so much so that you can tell the difference. At first it wasn't that noticeable to me, but after playing the Pro almost entirely (which I also like very much, and think is an incredible game by itself) before I spent good time on an updated LE (BIBLE & Premium)...I could tell the difference.

ACDC Pro
-The Pro model is faster, sure. Its not as immediately noticeable though when comparing to say something like Xmen Pro and its LE counterpart.
-No under-playfield, and as a result, gameplay is continuous.

The negative with this game is the Angus face. Its not terrible art...in fact its the same kind of artstyle they used in album art...the problem that its so huge. For the reduced price on Pro models, some will hardly care. Opinions may vary on this one. Same goes for the translite, although its not terrible photoshop.

ACDC Premium
-Premium and LE models have better looking translites, but opinions may vary.
-Color changing LEDs. With the new update, this game's particular version is ridiculous.
-The swinging "Hell's Bell"...the single biggest reason to go Premium. The ACDC Premium bell swinging via VIP pass makes it really cool to trigger on demand. The Pro model bell mod is able to recreate the swing effect, but only upon hit, and does not swing via FIRE button (maybe it gives you credit for a bell strike, but thats it on ACDC Pro)
-The Premium has a sweet metal ramp and adds to its value. The metal ramp feeds left ramp balls into the cannon via divertor. This doubles the time you can use the cannon during your entire game. On the Pro you only have the option to spam the right ramp to load the cannon. Not game breaking for some, but its something to notice for people like me who looks for some variation...especially since YOU WILL PLAY this game A LOT due to its addictiveness.
-Premium model's mini-playfield fire face area continues to get some love via updates (could probably use some more love from Lyman). Earning bell swings in fire-face underplayfield makes the game way more entertaining in modes like Hell's Bells.
-And finally, the Premium model's ACDC drop targets makes for more physics based randomness as the ball can smash into multiple drop targets via cannon shot...or have them triggered if the ball hits a drop target, and then dribbles south knocking more down.

As for the LE model negatives...the dancing band, 3D train, and detonator aren't necessary...kinda cheesy too.

++Both are great games, but 'for the money right now', I'd go Premium...especially since you can still get them at good prices and the price difference isn't as huge as say Tron Pro and Tron LE++