Compare to vs compare with

Compare to - is used to liken two things or to put them in the same category. You should use "compare to" when you intend to simply assert that two things are alike.Use "compared to" to illustrate that two things are similar

e.g -

1). The economy can be compared to a stallion charging at the gate.
2). I compare getting comments from students in class topulling teeth.
3). She compared her work for women's rights to Susan B. Anthony's campaign for women's suffrage.

Compare with - is used to place two things side by side for the purpose of examining their similarities or differences.Use "compared with" to illustrate the differences a comparison draws

e.g -

1). The American economy can be compared with the European economy to note how military history impacts future economics.
2). It would be interesting to compare Purdue with Ohio State.
3). Ann has a 3.5 GPA, compared with Jim's 2.9.

Source: http://gmat-grammar.blogspot.com/2006/09/compare-to-vs-compare-with.html