I mazed with two different explanations. One is in another link in GMATclub forum,
on "Compared to V/s Compared with". and another is inside sahil's doc.
Sahil's document says,
3) Compared to v/s. Compared with: To show comparison between unlike things, ‘compare to’ is used. To show comparison between like things, ‘compare with’ is used.
e.g. He compared her to a summer day.
Scientists compare the human brain to a computer. (Unlike thing)
The police compared the forged signature with the original. (Like things)
And aforesaid link says,
27. compare to vs compare with
compare to - use when two things are alike
compare with - use when two things are not alike
-- Which one is correct?

Thanks.