When i first started buying guns in the 90s, the 9mm was THE caliber to have, but when i began to learn about bullet performance , i.e. penetration + expansion ect, and what i felt should be the min. requirements, (12-14 in penetration with 1.5xs expansion ) , i found that the 9mm couldnt achieve the performance that i wanted . I then "discovered " the 40 cal , which easy to find a bullet that would do what i wanted it to do as there are many good rounds for it . i then added the 10mm to my list , an AWESOME round !
Time on the range as shown me how much better i can shoot the 9mm vs, the other calibers even when using the same gun such as the g19 and g23 .
With the improvements in 9mm ammunition i've now found myself buying 9mms again . they will do the job with proper loading . I'd rather hit an attacker three times center mass with a 9mm , then hit once and then miss two followup shots with a .40 .45 or even a 10mm. only hits count . just my opinion