GCSE/A level Sciences

IN MY OPINION it's chemistry, physics, biology but then that depends from person to person

because I think biology is mainly just memorization, and in physics if you know all your formulas and are able to manipulate them you're just about good to go, but chemistry involves both of these

Depends on the person’s strengths but:
Chemistry, biology, physics
(Only reason I put biology second is because although the content out of the three is probably the easiest, the exam technique needed for biology makes it a difficult subject.)

For me, biology is the easiest by far, then probably physics and then chemistry although last year it used to be the opposite

It’s different person to person. I find biology really easy, it’s mainly memorisation and then applying it to the question. Chemistry’s the next easiest, it requires very precise answers but once you’ve understood concepts it’s really easy and also exam questions are really repetitive so once you’ve done a few questions you’re basically sorted.
As for physics almost everyone I know agrees it’s the hardest, especially at A level. It requires you to understand a topic inside out and how to apply it to every type of question. The questions are rarely the same or similar in each paper so it requires a deeper level of understanding. When I was doing a level I was given university books aswell so I could read around each topic to get a better and thorough understanding.

For me I found biology > chemistry > physics from most to least difficult at GCSE. Though I found biology incredibly boring so that might have contributed.

I only did physics at a-level so can't comment on the other too. Obviously don't rely on what people say if you're picking because it's totally individual.