And here I thought this thread was going to be about GW figs (stat and fluff wise) versus GG figs...and, what's with all the hatin' on Space Hulk? Richard Halliwell's game is a masterpiece in its first edition, unmatched in tension, balance and playability. It is, however, very specialized and does begin to creak under the strain of expansions allowing for other situations than the presented bug hunts, before finally imploding with the truly aweful psychic rules of the Deathwing expansion.
Legions of Steel, with its added versatility, does suffer somewhat in playabiliy what with all the status markers and such, but certainly retains its balance and allows for a much wider range of tactical and even (dare I say it), simulatory options. It would be more fair to compare LOS to something like Advanced Space Crusade by GW or the Star Wars d20 Miniatures game by WOTC/Hasbro. Halo/Horror/Hero Clix probably has more in common with Space Hulk, as does Grindhouse's Incursion game or Twilight Creations Zombie. Note that I am firmly in favour of a massive mash up scenario featuring the figures from all of these games using the LOS rules set which I think is the only one that could encompass them all...