"Compared to" vs "as compared to"

Solution 1:

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:

Microsoft has a large market share [as] compared to Apple.

This question is difficult [as] compared to the previous one.

Or use the comparative adjective, and replace as compared to with than:

Microsoft has a bigger market share than Apple.

This question is more difficult than the previous one.