I'd say keep the .40, save up and get yourself a .45, then maybe down the line decide to sell your .40. Like someone already said, if you like your .40, you'll end up missing it.
.45 is expensive to shoot but sure is fun. 9mm is my personal favorite handgun round, accurate and relativity inexpensive. Also I can shoot my 9mm (Glock 17) much better than my .45 (1911) or a .40 (I've only fired about 70 rounds or so out of a out-of-box Glock 22 though)
Besides if you keep them all, during the zombie apocalypse if you happen to encounter zombies on PCP that are impervious to the 9mm
, you'll have a .40 and a .45 to take them out. That way you can also draw your .45 and make a wise crack about how this'll stop them. lol. 
.45 is expensive to shoot but sure is fun. 9mm is my personal favorite handgun round, accurate and relativity inexpensive. Also I can shoot my 9mm (Glock 17) much better than my .45 (1911) or a .40 (I've only fired about 70 rounds or so out of a out-of-box Glock 22 though)
Besides if you keep them all, during the zombie apocalypse if you happen to encounter zombies on PCP that are impervious to the 9mm


















































