GCSE History or GCSE Computer Science btw for History is Edexel and CS is OCR????
There is no answer to that question which can be applied to all students. Some will find History easier than Computer Science; some will find the reverse.
Generally speaking, if you're good at maths and science subjects, you're likely to find Computer Science easier than History. Similarly, if you're good at writing essays, and explaining something with both depth and clarity, then you're likely to find History easier than Computer Science. However, even that will not always be the case.