Morning Ronyo, morning here in NM anyway. I have a CZ75B in 9mm and love it. Personally, I would lean toward the 9mm. I have 4-40S&W pistols and one carbine (Beretta). I enjoy them all however 9mm has some advantages. Dealing with less pressure is one. 9mm is so forgiving in pressures and load variability. I cast 102, 105, 120, and 125 gr. bullets for 9mm. So much fun to work up test loads in 9mm with all the old and new powders. In comparison, I cast only the 175 truncated for the 40S&W.
Secondly is the bulge issue you have to be aware of in 40S&W. Not a big deal as long as you are aware of it and properly size your cases.
Third is arguable accuracy. For me, I get a little more accuracy from 9mm.
Fourth is 'Kick'. Quite a bit of difference between the two. Some 9mm loads you can shoot all day and pick up the brass right by your foot.
Finally, if you reload, 9mm brass is a dime a dozen at ranges. I've picked up over 5000 cases in the last couple of years. 40S&W brass is usually available as well but not in the same quantity.
A fun decision for you! Good Luck