I see a lot of threads recommending the 13 over the 11. But I also see some comments that the fans on the 13 come on quite a bit more than the 11. Aren't some of you 13" owners a bit frustrated with the fan noise? Isn't that a compelling reason to go with the 11's? While the 13's are better than the previous generation, they still don't seem to be as good as they need to be in the noise department.