There are many solid choices for the .40S&W caliber. I'd lean towards the new Hornady Critical Duty 175gr load. It does very well in the FBI protocol T&Es & the Critical Duty line has a lot of + buzz from the shooting sports/firearms industry.
Other top .40 loads for carry or protection include the Winchester Ranger T(T Series), the Speer Gold Dot 165gr JHP, the Golden Saber 165gr JHP, DoubleTap Ammo's .40S&W line, Corbon's DPX & PowRball.
Some .40 owners/LE owners like the heavy 180gr JHP loads but I prefer the 135-165gr mid-weight JHPs.
What ever you pick, always use only FACTORY MADE rounds for carry or protection, no reloads or hand loads.
Here are a few great online sources for ammuntion; www.shopcorbon.com www.doubletapammo.com www.cabelas.com www.natchezss.com www.sgammo.com