I agree with the OP. I think the two should be combined. They are both a Galaxy S6 and neither are different enough to constitute 2 separate forums.
It's like saying the iPhone 6 and iPhone 6+ are too different to be in the same forum because the 6+ has a higher res screen and OIS.
The differences are so minimal that everyone is just posting in the S6 forum while this one goes widely unused.
When I think of an S6, I think S6 and S6 edge version which are exactly the same phone with the exception of edge notifications.
That is not enough to make two separate forums. Getting them into peoples hands wont change the fact they are both a galaxy S6 and you will still see 90% of posts under S6 because no one is using the Edge forum much.
I post nearly everything in the S6 forum myself because I noticed no one cares about a dedicated Edge forum.