No, they are not easier or harder. Grade boundaries are adjusted so broadly as many people get each grade in each subject. So approximately equal percentages of candidates get an A in geography, biology, maths, English, French, or whatever random subject you insert here.
Now within individual schools, this can vary - for example, in my school, we get fantastic results in my subject. However, we also have really small class sizes.
Why is your child talking about s6 subjects now? It’s still so early in the year. And what basis are you predicting they are an A/B student? Based off N5 results? Those tend not to translate to equivalencies at higher level.
Both those subjects are quite similar in terms of them being quite content driven, knowledge based subjects. Which means for those who enjoy rote learning, they can be considered to be “easier” - however, not all children learn this way, and the amount of content you need is way more than for some other skills based subjects.
What subjects is your child doing in s5? And who is recommending these subject choices to them? What subject does this teacher teach? What are your child’s goals after school?