Author: Tero Heikkinen. Based on an original by David Webb.
ZX Spectrum 48K:

Space simulation as serious as "space invaders" combined with an over-the-top storyline of science fiction meets real history, provoking more questions than it even pretends to answer, Starion is one weird mess and a piece of gaming history nearly forgotten in the shadow of That Other Space Game. (No, not F.O.F.T!)

The Spectrum version is the definite one, and Amstrad is nearly identical.

Commodore 64:

This version is SHIT BEYOND BELIEF. It really has very little in common with the original. It is so slow that even with 200% speed increase it was slower than the Spectrum and that is just one of the lesser flaws. I don't think it is even proper 3D, turn right and the wires and dots wobble in chunks so that it is impossible to align the enemy to your sights. All this is obviously due to the technical inferiority of the c64 platform, so you can't really blame the authors...

Amstrad CPC:

I had to check this out, because I had a nagging feeling it has something in it that the others don't. And yes, it has an option to save the game to tape which seems to miss from the Spectrum version. Also the radar has a small picture of the ship, as in the C64 version - helpful for novices! Whether it plays a bit faster than the Spectrum one I can't tell straight from an emulation, I have never seen an Amstrad in my life so I would not know. But apart from the color scheme, this could be the best version.