Inspired by an argument I was in last night...
Is using performance-enhancing drugs cheating more than a pitcher doctoring the baseball? Both are illegal under the rules.
I maintain that doctoring the baseball is nowhere near the level of steroid use simply because no pitcher can successfully scuff every ball they throw to every hitter during every at-bat. A player who is on steroids has an unfair advantage every time he steps into the box. A pitcher who puts a little moisture on the ball or can scrape a rough spot is taking a much bigger risk of getting caught, since the ump is handling every ball he throws, and therefore there's no way to do it on every pitch.
Are they both cheating? Yes. The thing is, though, a hitter knows when he steps into the box that the pitcher COULD scuff a ball if he thinks he needs that edge during that at-bat, but it's not a guarantee. A pitcher doesn't have that luxury when a hitter on steroids comes to the plate. When Giambi, Bonds, Palmeiro or Canseco stepped into the box, their cheating was already in effect. There's no way to decide not to use steroid-enhanced strength. That's why they're different: steroid users cheat every time they step onto the field.