Binos like these are not much use for planets. My observations of Saturn and Jupiter in this case were from light polluted skies, but that does not matter with these very bright objects. You are better off getting a good binoviewer for planets... or there are some very expensive long f-ratio Japanese binoculars you can get, but the aperture is still small compared with even a modest scope.
the 20x90 is 10mm bigger in aperture than the 20x80 obviously, but I suppose you mean length.
They do seem a bit longer but it's only really apparent when trying to use hand held (silly thing to do
).