I actually see both sides of this argument.
I see why Buffdog, myself and others still like the 1st line with 81 and 55 despite what the advanced stats say.
I also see the argument that it's not shitting on Bambi and KFC to want to have them playing on seperate lines to see if we can get a bit better offensive balance and maybe have 2 lines that give up a little less.
At the end of the day, I accept that those 2 will play together, for whatever reason. They have obvious offensive chemistry so at least part of their game works to the Jets benefit.
The one thing that does baffle me is what happened to Mark Scheifele? Obviously I still love the guy but do you remember when he was a 200 foot player? What switch went off in his head that turned him into a guy who give 50% effort defensively? I think it might be too much ice time to be fair, but you deffo don't want a disgruntled Brighteyes loafing around the ice.
I am able to understand the arguments for keeping 81 & 55 together. I think they are mistaken, based on the limited samples we have of both of them playing apart. With the caveat that the samples are limited it appears that both of them actually score more when not together AND the sum of the defensive play is also better.
If we discard that conclusion, for whatever reason, then the larger sample seems very clear that the net effect, both O and D, is still positive if we either break up that pair or add Ehlers to the right side.
I have theorized that it is Scheifele's preference that keeps them together and that may be the best argument for the status quo. As you state in your last sentence, we don't want a disgruntled Scheifele, even if he wouldn't go so far as to deliberately loaf around the ice.
I'm still waiting for Vilardi to be the catalyst that makes that line work. Maybe next game.