I personally think stock is amazing for almost every situation.
Diamond back is probably the best for teams with Engineer spam or if you’re a good backstabber to get them crits!
The Ambassador is good for you if you’re good at shooting heads close range, other than that, it’s not very good.
L’entranger is good if you’re having trouble with running out of cloak. It’s damage penalty isn’t really noticeable, but it still cuts 15% damage off your weapon- so don’t rely on it too much.
Enforcer is good for situations when there’s a low heath enemy and you’re able to almost kill them in one or two shots- other then that, yea.
I hope I helped somewhat! I personally think stock is best since that’s what I use in most situations as spy!