just your regular Quick Ambitious Diligent Patient 30 Intrigue Illusive Shadow Spymaster.
Ambitious people are likely to murder to favor their clse family, ie your kids with your other wives to move them up in inheritance line as well as pretty much anybody that you would inherit titles. Sometimes it's fun to see an ambitious AI married in a distant realm murdering its way through inheritance for it or its kids. Spymaster have a drastic increase in plot power against people in your court
Also as noted, you get stat boost from wife or regent but it can't add to council stat boost so from a purely mathematical point of view a councilor with 16 intrigue or more will give you more intrigue than just your councilor wife (although it's sometimes still a good idea to have your wife as spymaster because the 100 opinion means she will never plot against you which is handy when everybody hate you).