Most likely car. It gives us flexibility, since we wouldn’t be in a terrible hurry. Of course, getting there by plane in a few hours, compared with a few days, has a certain appeal. Not only would we be traversing all manner of hill and dale and urban areas, needing places to stay, spending money on food and fuel and tolls to get out there, we’d have to do the same on the way back– unless we took a different route and really turned it into a lengthy sojourn.
We’ve occasionally talked about how nice it would be to take the train across Canada, maybe make our way to Alaska, but that’s a pipedream. A transcontinental excursion by car might probably maybe be more likely.