I have the regular sockets (not swivel/universal) in the Mac Spherical (Spline) and I really like them.
Spline seems to be either a love or hate on GJ. I use mine a bunch. I only bought them because I got the set for $10 or $20 out in my travels.
I also have all the splines that Snap on makes, and I like those too.
Some guys say they dig into the fastener and get stuck a lot...IIRC it was from someone in the rust belt?? That would make sense. Out here in dry so cal the hardware is in good shape and I have not had them stick. I haven't noticed any marring either.
Spline also gets a bad name because of the ******** cheap tool kits that have the splines that are supposed to fit SAE/MM and every other gimmick they can think of.