Plus if you are on the same PNR you and your companion get the lowest traveler's priority. Thus the two of you will go to the bottom of the list and will very rarely get upgraded. If you split the PNR you will get your FO priority and he will get the lowest priority and pretty much never get upgraded. I have had companion upgrades clear once and the companion was on a full Y ticket. I wouldn't buy a more expensive ticket K for very many desinations in hopes that you get a companion upgrade.

Welcome to FT!