With 15 years on the streets of a decent sized ubran department, I have finally settled on these for everyday carry.
The Smith is an older one and obviously it is used as my pry tool more than a knife. There hasn't been many doors it hasn't been able to open.
It stays tucked behind my magazine pouch. It is is sharp and can be used if all else fails.
Your defensive knife should be carried on the non gun side to allow you to keep a hand on your gun to prevent the bad guy from pulling it out while deploying your knife to stop the threat.
The Spyderco Gayle Bradley is my defensive knife in case there is a fight over my handgun. Modified to act like the wave it allows for one hand opening while in a struggle.
If your son in law is a righty the Gayle Bradley will allow him to move the clip to carry it in his left pocket.
Lastly the ZT0350 goes in my left pocket and is my go to knife for any normal cutting duties.
I also carry a Gerber multi-tool on my belt as well. It gets used a lot to tighten door knob screws, cut wire, and generally is my tool box in a pouch.
I've carried Emerson, Spyderco Police and Military, I've found the versatility of the Gayle Bradley to be the key to for me.