New strings are always better. Are you sure you didnt change the thickness on the strings? Going from 0.9 to 0.10 can be a living hell in the start
Just the opposite for me. If I put a 9 on, my thoughts are "this is awful".
Very different sizes. I realize that all with the most rudimentary level of education understand this, but you may not have thought about it.
The size of a cross section of a cylinder is radius squared x PI. As PI is a constant, the radius is the factor to consider. Here we have strings with radius of 9 and 10.
9 squared = 81
10 squared = 100
so a 10 is almost 25% more massive than a 9.
And it gets worse with an 8. A 10 is over 1 and a half more massive than an 8.