I think a pretty solid case (pun intended ) can be made that the 40 actually BLOWS, not sucks.
Of course that applies to all cartridges as they blow bullets out barrels, not suck them out. It seems to work better that way.
While I don't think the 40 is anything better than 9mm, 357 Sig or 45, I don't think its worse either. All pretty much a wash effectiveness.
At that point it really boils down to what you like and even more importantly how you shoot it (though I think we tend to shoot what we like better than what we don't like).
9mm is nice in that it allows you to not have to grab an extra clip and still have a lot of shots (or lets you recover from shooting badly and have rounds left to do something with your new found conscientiousness)
Did we need 40? No. Are hurt by it, no. If you like it, cool and good shooting.