The question of whether the Samsung Galaxy S6 Edge was as good running on Marshmallow as the S7 is, so is it?
The Marshmallow update does help to boost the speed of the Samsung Galaxy S6 Edge, with the handset running on the OS as it offers the Exynos processor.
Touchwiz is known to not be the fastest UI on a handset, which is on both the Samsung Galaxy S6 Edge and the Samsung Galaxy S7, both running on the Exynos processor.
Bear in mind that you can get the S6 in both the edge version and the normal version, as you can with the S7. But whether or not the S6 Edge with Marshmallow installed is as good as the S7 remains to be seen, as the S7 is the newer handset.