They're different.
A - Cleaner, less hazy, poured with a slightly tighter head and possibly better lacing.
B - Slightly more aroma, more bitter, more hazy.
My own experience with open fermentation is there's a difference, but its a broad, qualitative difference. Not so much as getting more intense esters, as getting a broader more complex array of esters, using yeasts that express more. Fermentation is better, with less off flavours and less maturation needed, resulting in a better fermented beer. Better clarity. And reduced bitterness through more vigourous fermentation.
Which is which? This is where it gets tricky and where I probably fall on my sword. Tricky because Notty is very clean with very little ester profile, which mitigates some of the advantage of open fermentation. And, also with the carbonation issue, with foam being a carrier for aroma, that might subdue any differences.
Notty.
My overall impression is that A is the better beer. It's slighly less hazy, cleaner tasting and more balanced, it just tastes like it fermented better. B tastes greener, has a slight green apple aroma and is more bitter. My feeling is that the green apple aroma isn't esters from Notty, but acetaldehyde from fermentation.
So, with trepidation, I'm saying A is open fermented. Less stress on the yeast making a better beer.
I wouldn't inflict my Altbier on you but more than happy to send you something in return 
of deciding which is which.
