personaly, i am leary of the spline drives... would stick with 12 point as i know they were designed with only 6 and 12 point in mind(fasteners)... same tokem, i have never used a spline drive socket/wrench to have a valid opinion on how well they do or do not work... just my 2 cents
that is a good illistration of spline on spline... op is asking as reference to not purchase deep 12 point sockets... what would the contact angles look like on the 6 and 12 point nuts/bolts.....
the best thing about a 12 point socket or wrench is more possible positions on a six point fastener... sometime you are working in a confined area and the 12 point will just get on the fastener easier...
I have been using both 6 and 12 point sockets. The 12 point sockets are used the most and they will work on hex, square, and 12 point fasteners. One reason I like 12 points is they don't have to be rotated as far as a 6 point to line up with the fasteners. So far I have not encountered any spline fasteners. Maybe I will buy some spline tools if, and when I encounter some spline fasten
spline head ratcheting wrenches fit both 6 and 12 pt. Grips the bolt like it was glued on.