Ahh but this is precisely because Marines are forgiving, especially to new players, and tend to be taken for this reason which leads to a higher ratio of Marine lists. Which again leads to lists tailored to take down marines. You don't see players gearing to kill Guard in specific simply because the number of Guard armies is substantially lower than Marines and Marines being what they are are simply a harder army to deal with. Make a bad mistake with Guard and you are screwed but make that same mistake with Marines and you are still going to be able to recover due to the nature and stats of the army.Plus the whole "Marines are forgiving", what? Every competitive list is designed with MEq killing ratio's in mind. When someone chooses a unit they don't think "How many Guard will this kill?"