I'm not sure about the beamer, but the silenced manticore is nice for those knife situations. tap-tap-tap-knife = dead before they can react... and is faster than two knifes. I would imagine the Beamer silenced would be just as good. I think the biggest thing with pistols is whether you need it silenced or not. The underboss & commish are nice, but put you on the minimap. As a LA, I like to do hit and run and constant movement and don't want to give away my position. (same with taking down spawn beacons (which I switch to pistol to conserve primary ammo).
When asking what pistol to get 6 times out of 10 you'll get one of the revolvers as your answer. But since you are Vanu and enjoy silencers and sneaking up on people as LA I'd say the Cerberus isn't a terrible choice. 2 shots + knife will do the trick, especially when one shot is to the back of the head.
It's a good idea to assume your opponent has Nanoweave 5. If you don't shoot them enough times before knifing them, they're more able to finish you off. This is especially true if they know you're there or if you're using a gun that takes more than two shots. https://forums.station.sony.com/ps2/index.php?threads/pistols-knives-and-you.148810/
