I'm not a lecturer or moderator or anything, but as a fellow student, the pros and cons of doing 10 units (as compared to 11+ units) are as follows (imo):
Pros:
Doing 10 units means you have more free/study periods at school, which you can utilise to concentrate and study for all your subjects, however, some students end up bludging or wasting these periods, so it's a matter of self control. You're also able to put in all your efforts into 10 units, rather than putting energy and hard work into more than 10 units, some of which wont even end up counting for your final atar
Cons:
You have no back up plan, so if one of your subjects goes "wrong", e.g you stuff up an asssessment, or something happens that causes you to not perform as well as you had planned, you can always rely on your other units instead, which is why doing 10 units is considered risky
Personally I do 10 units because I'm very invested and fairly confident in the subjects I have, and I enjoy them a lot. I also use my frees to my advantage to revise or do homework as much as possible, so that's helpful because I have more free time to revise at home!
But yeah, that's my 2 cents