If you're referring to the speed value of the weapon, I don't think that's a representitive of the actual speed of the projectile, it's more firing speed. A laser being a LINE in semi-unrealistic: large, heavy lasers take a lot of energy to fire once, let alone holding a stream.Plasma's different, at least in game terms. Example:
Warhammer 40,000. (groan!)
You have plasguns and lasguns in 40K. You also have plasma cannons and lascannons in 40K. The Lascannon has a strength of 9, AP 2 (might be AP 1, but I don't think so) on a 1-10 scale (VERY powerful, only one other race and reliably get a stronger weapon AFAIK). It's essentially an anti-tank gun. Fires normally, just like other weapons. Plasma cannons are strength 7, AP 3 (again, guessing, it's been a while). They're weaker, but they use blast templates. A plasma cannon can cover a wide area, whereas a lascannon fires a narrow beam. (Plasguns and lasguns are different from their big brothers, BTW: lower strength/AP and the plasgun dosen't use a template.)
However, Penetrate is a great idea. Obviously, it can only really work for some attacks, but, say if a creature is damaged badly enough, a beam from your laser rifle or a sniper rifle slug might just punch through it and attack the next in like (at reduced damage, of course).