Originally Posted by
gglave
You can't really 'drive along the coast' from Vancouver to Seattle (you can in some portions, but it's very convoluted and complicated).
A lot of the drive looks like this:
https://goo.gl/maps/oqZLk
and this:
https://goo.gl/maps/gCvJ5
By contrast, the train hugs the coast and is very scenic.
Also, parking the car in downtown Seattle will be an expensive proposition, even when you factor train fare into the math.
Sounds like the OP is going to explore the city, not hang about a railway station for 10 hours. Sounds like a great use of available time.
.....but the OP will have seven days in Vancouver several days later. [It would be different if this were the OP's one and only chance to see Vancouver.] There's no need to rush around playing tourist right after getting off the plane. I'd rather relax than run around the city immediately upon arrival, especially when it means arriving into Seattle (and my hotel room) fairly late at night the first day.