Temperature, temperature gradients, heat, membrane potential, charge/discharge speed, etc, are all variables in long term battery life, along with dozens of others.
So I'm reluctant to agree or confirm with any sweeping statement about a single variable (in this case, heat generated by charging), because it may be true in some cases but not in all. And it also depends on the specific battery.
Most likely, for most laptops, for most daily use-cases, and a charging pattern of 90-50-90 in 2-3 hours, I'd rather take the slightly increased temperature than keep the battery at 100% for that time period.
But again: it depends. On so many things.
Edit: also, either case (keeping at 100% for 3 hours vs 90-50-90 for 3 hours) is better than keeping at 100% 24/7. So no harm done if you can't decide which is better. Just A) don't plug in all day long and B) don't go crazy with the heat and you'll be fine.
So I'm reluctant to agree or confirm with any sweeping statement about a single variable (in this case, heat generated by charging), because it may be true in some cases but not in all. And it also depends on the specific battery.
Most likely, for most laptops, for most daily use-cases, and a charging pattern of 90-50-90 in 2-3 hours, I'd rather take the slightly increased temperature than keep the battery at 100% for that time period.
But again: it depends. On so many things.
Edit: also, either case (keeping at 100% for 3 hours vs 90-50-90 for 3 hours) is better than keeping at 100% 24/7. So no harm done if you can't decide which is better. Just A) don't plug in all day long and B) don't go crazy with the heat and you'll be fine.