The EA7 has fixed content on each screen and works well once you get the idea how it works ..the EA7 has no video output..
The BK9 has a switchable screen button and allows some modification..
It works well but I think the EA7 dual screens has an edge.. The BK9 does have a video output..
I will add that the Roland
DUAL Screen concept at first was a bit weird, BUT, once you understand it and get used to it makes a whole lotta sense especially when performing Live..