Imo.
Chem > Phys > Bio.
Im in year 11 too. Personally, I find physics a walk in the park. It's so easy! The hardest topic you'll probably do is motion. You have to put a bit of hard work into that. Lots of memorizing there. But other then that, goshh, things are easy.
Chemistry on the other hand can get hard. Besides all the memorizing of chemicals and their valcenies you have to do, you have to also get your head around the process of equations and their formulas. Now that gets tricky. But chemistry is simply amazing! The things you learn is just !! (l)(l)(l) .....explains the world.
Do chemistry, if you dont like it, go to biology.
But at the end of the day, it's all about how much effort you put into that subject.