Jasper is what Banff was before everybody found it. The same glacial water and the same scale with a fraction of the traffic, and that is the whole argument for making the longer journey. Maligne Lake, Pyramid Island and Athabasca Falls are genuinely quiet on a weekday morning in a way nothing in Banff has been for a decade.
The cost is distance, and it is not a small one. Everything in Jasper is further apart than the map suggests, and the Icefields Parkway between the two parks is three hours of driving with no shortcuts and, for long stretches, no signal. A timeline built on Banff assumptions does not survive up here. Guests need telling plainly how far it is before they book flights.
Jasper is a designated dark-sky preserve, which is a real photographic product rather than a brochure line. On a clear moonless night the Milky Way is visible to the naked eye from the lakeshore, and a portrait under it is something almost no Canadian wedding gallery contains. It needs a clear forecast, a moon phase checked months ahead, and about forty minutes of everybody's patience.