I have done both boards and honestly cambridge is extremely tough especially when compared to edexel. Id say it depends on the country. In my situation, I was doing edexel, when I was shifting, the other country also allowed exams of Edexel so it wasn't much of a problem as I countinued with it. But in your case, if you will be eventually be switching studying for the edexel to the cambridge exam, I would definetly say to start revising according to the cambridge exam because those are very hard. And also, if you will be eventually switching boards, it is the only logical thing to do really, start studying that board now. Any other questions feel free to ask. And Good Luck! (You're gonna need it)