Orc Attack is one of those cases, where Atari shows its brilliance, in comparison to the other versions of the game.
The C64 version is not too bad, but it is like a somewhat stripped and dulled-down version of the game. Playable, and fun for awhile, but feels like something is missing.
The Atari version has it all - GREAT flame-effect (The flame you drop looks good when it falls, and then bursts into waves of fire in an awesome and satisfying fashion, it's so wünderfyl!) compared to the pathetic C64 attempt (the ugly and darkly colored, small piece of crap slowly crawls towards the bottom of the screen, where some dark goo seems to lazily spread, yawn), the Wizard looks cool and is actually animated, dropping bombs on those skulls remind me of old Atari 2600 games, like Crackpot and Kaboom!, and the sound effects are so 'video game perfect' that one couldn't ask for better ones.
Playing this on Atari 800 XL, and then immediately playing the C64 version on a C64C (no emulators for me when it comes to Atari 800 (etc.) and C64, unless I can't get something to run on the real machine) makes the player realize that something is definitely not right with the C64 version. Something is a bit 'off' about the playability and speeds, and perhaps even the difficulty curve.
But the worst offense is the awful C64-wizard - what, now he shows his face? He has a black, ugly coat, and he just stands in a pose, shooting black crap at you, so you don't get to experience the 'Crackpot' simulation? He looks so ridiculous, his pose is so stupid, and he stands in a weird place - a bit too right to be on the 'side' of the screen, like the Atari's Wizard so immersively conjured his spells, and his clothes are just black and ugly.
What the heck went wrong with the C64 version? This shows you that the original is often the best, and the conversions, clones and copies play a second fiddle. Contrast between these two versions are at least as big as the contrast between the C64 version and the Amiga version (which is not official, of course, but it was my first exposition to this game).
Speaking of the Amiga version, which is gory and all that, I don't think it comes close to the Atari version's perfect playability.
As for the sound effects, the C64 effects are good, but the Atari sound effects really shine.
This is one game that is so clearly better than the C64 version (and the Amiga version), that there can't even be any debate about it - I completely and utterly recognize the glory of this Atari version. And anyone that honestly conducts the same experiment I did, is forced to do also, by their own sincerity and the truth itself.
A great classic! Only after playing the Atari version, do I fully understand the goodness of this game. Atari's red looks really good compared to the C64's red, by the way, when you look it side by side - at least with this game.