The writing experience doesn't get any better than this supposedly!
If you look at the photo below, realize all three nibs have the exact same job. And they're written by the exact same user (me). The nibs are kind of flexible (very slightly flexible) and they act as a damper or shock absorber when you write. Thus, a bigger nib can absorb much more shock than a smaller nib. Thus, the pen on the far left, which is a #4 size nib, sometimes feels a little firm and a little stiff. The pen in the middle is a 146 with a #6 nib, this is my daily user pen and it feels very comfortable to me. And on the right, the pen is the 149 with the #9 (largest by Montblanc) nib - this one might feel even slightly more supple than the #6 even! While I personally don't feel a huge difference between #6 and #9 (hence why I recommend to most people a #6 is good enough), I do feel a substantial difference between a #4 and a #6. So I often recommend to many to forego the #4 as it might feel slightly stiff. HOWEVER, some people like the stiff nib! Especially if they're making very small characters in Japan or in China - that stiffness increases precision. So there's a lot of personal choice here.
You have the great fortune of having a #9 in medium which is a delightfully smooth nib. What a wonderful writing experience that must be!