If you are looking at itineraries on only Koningsdam and Nieuw Statendam, then you need to look at videos or photos of only those two ships. A Signature Suite or Neptune Suite on Koningsdam is different to a Signature/Neptune on Eurodam, which is different to Signature/Neptune on Rotterdam. All have the same naming but different sizes, features, facilities.
On Koningsdam we have been in both Verandah Staterooms and Vista Suites. Main differences are that the Vista Suite gives double mariner points for the number of cruise days, and has binoculars in the cabinet. Not much else.
We have had an Aft view Vista and we were not impressed with the 'ride' while at sea (shimmy) and have been quite happy with Verandah Staterooms in our recent Koningsdam cruises. We have found recently that Vistas are not worth the extra money over a Verandah stateroom.