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: