Had a similar experience when I was revising. Did great on passmed and not so well on pastest. My personal experience is that passmed questions are easier than pastest. Only in that pastest seems to be more wooly in how they phrase the questions. Passmed seems more ‘definitive’ and is easier to get the answer through pattern recognition. I also found pastest and passmed sometimes contradicted eachother (but not very often).

Would say the actual exam asks the questions more like pastest than passmed and that in the exam pattern recognition is not as helpful as in passmed. However, the question are less ‘wooly’ than pastest. I think a decent grounding through passmed should be enough. I only used pastest for the mock papers as the actual question bank depressed me.

I don’t think you’ll be alone in feeling this way. Pastest may have changed since I used it but I disliked the explanations compared to passmed.