I prefer the PCE variant: HELLFIRE S.
Both are rad, tho.
The PCE version Hellfire S is nice because it has cutscenes and 2-player mode and the Genesis version Hellfire does not. This is strange because the PCE only has one controller port - you need an adapter for the second player - but the Genesis has 2 controller ports built in... go figure A lot of people think the Genesis version is better in gameplay, but for me the PCE version gets the nod for the 2-player support.
That's the perk of a CD-ROM disc over a normal ROM cart.
The Genesis/MD port of the game is a bit strange. It has some new graphics and the giant laser cannon which didn't exist in the arcade original. Gameplay wise the PCE version is far more faithful to the arcade, but lacks the parallax. Both ports are cheap enough to try both and see which you prefer, but the arcade board is certainly the ideal version if you can.
It's a great game to have in my collection as far as MD/Gen carts go, but it's definitely not one of my Toaplan favorites. Keep in mind I've yet to play the PCB/ arcade ROM or PC-E port. I do love Hori's though, and I love Zero Wing.
Is it fair to call Andro Dunos Visco trying to do Hellfire? I do like Andro Dunos quite a bit.
If you want to know my opinion of the PC Engine version of Zero wing, read this article that I wrote about it over at Pcenginefx. Great game, just...