Concerning dry hopping: This lid is very easy to get on and off. If you are worried about contamination within the 4 seconds it takes to dump in some hops, then you could just crack the lid up half an inch and scoot them in there, then this lid would pose less open space than a cornie lidNeither is a worry unless you ferment in a bio ridden and infested bacteria lab.
I still like the cornie lid but that may also be because I am accustomed to using it for additions and what not. If you have not used one it may not be an issue.
I am also not sure how lifting the lid to put in a hop bag of hops will open less space than a cornie lid.
For me it would come down to price. The one feature that I like the most is the ability to close it up and throw a spudding valve on there and carbonate in the vessel.
How is the comparison going to work? Will you brew 2 batches and ferment both in different conical. I have skimmed this thread mainly looking at pictures so if I missed it I apologize.