Are both "compared to" and "as compared to" correct?
- Microsoft has bigger market share compared to Apple.
- This question is more difficult as compared to the previous one.
They are both correct, and different ways of saying the same thing. However, neither way fits in your examples. It is ungrammatical to use a comparative (e.g. bigger or more difficult) with compared to. Either use a non-comparative adjective (e.g. big or difficult) with as compared to or simply compared to:
Or use the comparative adjective, and replace as compared to with than:
"As compared to" and "as compared with" are grammatically incorrect. Correct usage for comparisons of two things is either "compared to" or "compared with," according to the Merriam-Webster English dictionary. "Compared to" refers to two things that are not alike, and "compared with" is used to refer to two similar things. Insertion of the word "as" before either type of comparison is incorrect.