Is it better to become a nursery assistant or a teaching assistant in a primary school?

I am thinking of taking a course and I want to know what is better for my career path. I am based in the UK. I can’t decide which way to go, whether to become a nursery assistant or a teaching assistant in a primary school. I really like nursery age children, but I heard that they work long hours and for little pay. I am not sure whether working as a teaching assistant is complicated, what kind of work does it include? Do I have to have perfect numeracy skills for that? Do I have to work with the whole class on my own?