pick whichever appeals to you most, I know people who do both. CAFS is very straightforward, the content isn't something which would personally interest me but obviously that's a very subjective viewpoint. In terms of difficulty, I'm not sure, I would assume pdhpe is harder from what I have heard.
I'd suggest looking through their respective syllabuses and making a judgement purely based on interest, perhaps even look at a past paper or two to get a grasp at what you're getting yourself into.