Hmm... never heard of human being considered harder before. If you want to do a degree in biology, I would do higher biology for sure, I would imagine it would relate better to more aspects of your degree. I was told by a careers advisor (feel free to shoot me down) that higher is better respected by some of the more prestigous and 'old fashioned' universities, don't know how much truth is in that though. TBH human biology would suit my career choice far better, but I decided not to go for it for the reasons above, plus I wanted to do advanced higher (my school doesn't offer advanced human, does it exist?)