Not to rain on the parade but I wouldn't be worried about a sidearm at this point in the game if you haven't even started schooling yet.
There's gonna be a lot more other stuff your gonna need to remember.
If you graduate and get a job you'll be issued a weapon, also then depending on the department you can find if/what they allow for personal weapons on or off duty.
Since your leaning to the .40 I'll go ahead and say 9mm is better because its more affordable to shoot and has an easier learning curve thus letting you practice more and become a better shooter. I've found alot of novice shooters gravitate towards the .40 for some reason... Probably cuz the 'cops use it.' Odds are you'll be issued a .40S&W anyway so I wouldn't sweat it.
E-Shock rounds are engineered to expend maximum energy into soft targets, turning the density mass into an expanding rotational cone of NyTrilium matrix particles, causing neurological collapse to the central nervous system.
- Yeah I can do that.
I guarantee you will know it if a bicyclist hits your house going 1000 mph. -Smaug