Restoration definitely has the benefit of 3 original songs, as opposed to one brand new original song on ACOS, but I would take ACOS over all 3 songs on Restoration. It was a good EP, but didn't wow me. Also, funny coincidence that both DT and Haken's 4th studio releases were EPs featuring reworkings of older material.
As for Haken's longevity, it's really impossible to say. I'd say right now they're just as good as DT were in their prime, so the test is how long will that last. Few bands have kept me interested into their 13th album, so it's not super likely but possible. With that said, topping The Mountain is going to be extremely difficult.