Guns....
In the $400-600.00 USD range, Id suggest these choices:
The new SIG 320 semi auto series.
With a new 320 pistol you can quickly add or change frames, trigger types, calibers etc. SIG Sauer re-engineered the older P250 line and upgraded a few points. With one 320 pistol you can switch to 9mm, .40S&W, .357sig etc. You can add a white light or laser aimer. It's robust & geared towards US law enforcement & SWAT types. I like the new OD frames.
The Glock 22 or 23 gen 04 .40 is the same as the 320 series. You can buy after market magazines, barrels(special conversion types), parts then shoot 9x19mm, .40, .357sig, .22LR. It's fast and easy to switch.
If I didn't buy my Glock 21 .45acp gen 04 I would have purchased a LE trade in Glock 23 .40 gen 04 with a 9mm conversion barrel. The 23 is my first pick, the 22 is okay but a tad bigger. Either .40S&W Glock model could suit your needs.
The S&W Military and Police series is a big seller for Smith and Wesson. 1000s of M&Ps are out there, defending CCW holders, security guards, cops, etc.
I was thinking of buying a new duty M&P .40S&W full size then obtaining a after market conversion barrel for security details.
My state mandates re-quals with the caliber on your security license(armed).
I'm looking into the new micro dot & RMR type pistol sights. The S&W CORE models seem to fill the bill. The new Glock MOS models are good too.
Rugers are a good value for the $400-$500.00 market but I think you'd get much more benefit from a Glock 22/23 gen 04 or a SIG-Sauer 320.