I do think it's a bit futile comparing records like that, even when you're comparing managers with similar length of service, because every clubs situation and liklihood of relegation is different.
I don't think Rodgers would've got us relegated as it happens, but we would've been looking over our shoulders for the rest of the year. I don't really think Coppell would've done much better this season either, largely because he didn't want to be here and wasn't up for the fight.
That comes over to the players and they drop off with it and I'm sure that had a lot to do with our downturn from finishing in 8th (and not showing the ambition and drive to go for Europe) and then eventually throwing away automatic promotion with dire form post New Year 12 months ago.
It may well have been very different under Coppell, but I don't think it would've been any better in the short term and certainly not in the long term.