is there any difference in difficulty between them?
Yes
Some people are saying that mocks are easier and some that exam is easier, which one is true?
From my own experience schweser mocks are a bit tougher than cfai.
Schweser mocks are tougher and have a different feel, especially ethics. I have done badly on the ethics portion of Schweser mocks but done well (most of the time) on CFAI mocks.
I find that CFAI is a bit more “fair” on ethics than Schweser in the mocks. I feel like third party providers just go through the ethics section and try to pick out sentences they think people would have forgotten and hinge questions entirely on them. Whereas CFAI wants to make sure you understand the heart of the Code and Standards.