There is no definitive style for Slaine
Definitive versions - well there is a can of worms right there.
Basically there are three categories as far as I can see.
Stories with multiple artists and no one definitive version, examples include: Dredd, Sinister Dexter,Slaine
Stories with a single definitive artist( or with more than one artist but where one artist has so dominated it as to claim definitive status and relegate all others: Strontium Dog, Ace Trucking, Robo Hunter, Kingdom, Brass Sun, Jaegir, Zenith, Halo Jones, Harry 20, DR and Quinch
Stories with Multiple artist but which none the less seem to still have a defined look ( i.e the artists managed to make the look of the characters consistent): Rogue Trooper, Bad Company, the VCs. I would even put ABC Warriors in here, which seems to pull off the remarkable feat of having loads of different artists whilst still leaving me with a single consistent idea of what each character (apart from Col Lash) looks like.
And to buck the trend we Nemesis and Nikolai Dante which despite having had many artists have TWO definitive, equally valid versions.
Anyway I am sure this is all subjective and others will have different views(especially on ABC Warriors - Pat Mills canned it after series 1 due to frustration at lack of a consistent artist ).