Since I own and have shot both, P9 and P40 Covert, if I could only have one it comes down to tolerance for recoil. The P9 is a pussycat, it's a girlfriend gun. No offense ... my g/f handles it well since she can't manage the 12 lb trigger pull on most snubbies. Expert kick boxer with weak fingers ... go figger
Recoil on the P40 with full power loads is snappy but not what I consider uncomfortable and doesn't twist my wrist on firing. I carry RBCB Performance Plus in my .40, 77 gr. TFSP 2100 fps at 754 ft/lbs. I wouldn't want to get hit with this stuff and you have to see what it does to a cantalope
http://www.rbcd.net/products.htm
I carry the P40 daily, usually in an ankle holster but move it to a strong side holster if I can cover it. Hope this helps.
And if you are thinking about sending one off for a carry package, get the base model cause any nite sites are gonna be trashed by the gunsmith taking them off.
--Mike