Guideline. Use compare to when your purpose is simply to liken — to point out the similarity (or dissimilarity) between — two things. Use compare with when your purpose is to analyze two things on the basis of their similarities or differences.
- You cannot begin to compare [liken] wakeboarders to water skiers.
- I would like to begin my speech by comparing [weighing one against the other] this year’s water skiers with the water skiers we had last year.
Source: Grammar for Smart People by Barry Tarshis.