Is it better to drive or fly from San Francisco to Seattle?

I don't live in or anywhere near either of these cities, so I would fly into one of those cities and either drive the coast or fly between the cities, and I want to go on the Pacific Coast Highway as well. The only problem is that it will take a long time driving, so I think I would take a train because I could go faster and less stressfully, but still see everything along the way. I've been to California before, but not Oregon or Washington, but I really want to go though.

Thanks A Hunch and Gypsyfish!! I've heard that the plane rides and the train rides along the West Coast are nice. Just like Gypsyfish said, I would probably take the train as long as there aren't too many stops. I would still want to see the big cities and major attractions along the way, but everything else would look better from the train itself. All 3 of the states have very nice scenery, and a view from the train could be as good as stopping at everything.

I think I would want to start at San Diego or Seattle and go down the coast stopping at the major cities and attractions along the coast (Portland, San Francisco, L.A., Big Sur, etc.), and would see San Diego and Seattle on my own. I've heard the drives are fun, but are pretty long. I think I would drive/take the train one way, and make as many stops as necessary and fly the other way, as I could see everything, but still make it shorter. Thanks everyone for answering!!

Overall, distance-wise, it makes more sense to fly between SF and Seattle, because the U.S. is a large country and it takes just a couple hours flying vs 12-14 hours driving, so I think I will ultimately drive/take the train depending on time and costs one way, and fly the other way. Flying the West Coast is cool as well, but driving/taking the train lets me see everything, so I would drive/take the train while going and fly back to the starting city.