How many did you test?
I once did a trial of 5 sisters from Buckfast Freidrichskoog against 5 Neuwerk and 5 Torfhaus-mated Celle line. This is still quite a small-scale trial but it was enough to show me that consistency was important if you ever intended to keep more than a handful of colonies (the workload would become too much if you had to inspect every colony every week).
Of the Celle line, island mated were consistently more uniform than mountain-mated and they developed colonies more-or-less-the same size as most of the Buckfasts. There was one Buckfast, however, that out-performed everything. The stack was so big that I had to build a platform to reach the top. Towards the end of the season, it swarmed. It was the only one that did.
Now, if I had an apiary full of colonies like this, I would get a huge crop - but, I would have to spend all my time managing that one apiary. That is fine if you only have a couple of hives - but not on a larger scale.
It's difficult to draw too many conclusions from this but I decided that I would rather have relative uniformity than massive colonies that I didn't have the time to look after.
I have moved on from Celle line. These are definitely aimed at the mass-market compared to the queens I use now but they are a good introduction to what carnica is capable of (based on over 15 years experience).