This has been said at least a few times and I think you’re one of the guys who’s mentioned it… but the D and the 4 breed so much better than the 91.
From a growers perspective the D and 4 breed better, for sure. There's less genetic variability in 91 crosses but more deleterious traits that will make it harder to fully express at the end of the day.
Not suggesting that 91 crosses aren't elite or desirable as I'm growing 3 crosses with 91 present, 2 from CSI.
Grew 6 or 9 snausages from seed. I selected a couple of heavily 91 leaning ladies, one with thinner stems that I'm predicting will be the winner.
Popped a pack of nuclear winter, missed watering a tray for a week or longer and lost a few plants... more pissed I killed 6 motor breath x sour dubb in the same tray. Still have a 91 and a snow leaner.
Also growing Arcata trainwreck x chem 91 from cannaventure, too early to speak on them.
Not trying to scare folks, just keeping it real.