As the loving owner of both Atari 800 XL and a Commodore 64C, I feel obligated to compare the differences between versions in my reviews / comments.
Astro Chase is one of those games that you have to really look at with a magnifying glass for hours to find all the little differences between the Atari and the C64 to be able to finally declare a winner.
Which you probably can't, anyway.
I just recently played both versions today, and I have to say, they are so similar, that I wouldn't blame anyone for having strong nostalgic feelings for either one (or both).
This was the first game that I saw having a wonderful intro sequence that got me all excited. The game itself, sadly, didn't quite reach the potential the intro sets up.
The game is very simplistic and repetitive, and I couldn't really care about saving the Earth for the fourth time, after nothing seemed to change.
But it's a good game to spend a few minutes in a simplistic, mindless, relaxing destruction of some attackers. And the explosive Pokey always delivers the satisfying aural pleasures.
The Atari version seems to be ever so slightly better than the C64 version.
First of all, in the intro, Atari doesn't have boring grey, which is a big part of the C64 version's color scheme. Second of all, the animated space pilot actually synchronizes the footsteps, unlike the ice skating C64 pilot, who slides while walking.
The crunchier Pokey noise wave sounds just fit this game better than the softer SID noise, and makes for a more massive experience.
Oddly, the space ship in the intro has a different shape, depending on which version you play.
The gameplay is pretty much the same, and just as repetitive and simplistic. There are simple games that are great classics, but this one is a bit too simple, perhaps. Also, not being able to stop your spaceship is really annoying, although you learn to play 'around' it.
All in all, a good little game, when you just want to have a quick, not-so-serious fun for a couple of minutes, and nothing much more. Even Orc Attack offers more entertainment (another game where Atari version shines over the C64 version).
Good game, but only in short sessions.