How dose this compare to the 40 and 50 performance wise? I have a No. 8, which is apparently the same as the one you've reviewed, but with a longer body, and it has the best ink-flow and fine lines out of any brush pen i've used. I was looking to upgrade and was wondering if it's worth spending a bit more money for a 40 or 50 or if i just shouldn't bother and go with this?