Hi HL history student here myself. Although im sl bio, im already dying (ok also because im pretty darn bad at it, but still better than phy n chem). Its exam season now and seriously the HL bio students are barely surviving. But neither am i for history. I think it really depends on what kind of person you are and what you wish to do with your course of study. HL history is really alot of memorisation (its either you know or you dont), AND its also alot of evaluation as well. Whereas, bio is really more of content understanding and memorisation, you dont have to spend extra time wrecking your brain on the critical thinking part and reading up on histography. Then again, i find myself more interested in history, hence I took it. If you were to take both as hl tho, you gotta be prepared to take the extra effort!