"the East has more history etc"
I wouldn't say that history is really the top selling point of the US in general 
There's definitely a difference in east and west coast culture (I'm married to a Californian). But I would say that of all the east and west coast comparisons, SF and NYC are in some ways the most similar. Wealthy, competitive, fast paced, hugely expensive to live in the city proper, small and densely populated, fairly diverse (NYC much more so), quite progressive with a large gay community, ostensibly Democrat. Though the obsessions are different - SF, technology - NYC, finance and fashion. NYC has more of everything, that's for sure, more museums that are bigger and better, more restaurants, more neighbourhoods with their own character. SF has much more of a history of leftist / alternative culture, particularly in the Mission.
Once you get out of the city, you'll feel the cultural difference even more. SF you're in central California. You can ski at Tahoe, hike and camp in the national parks (Yosemite), surf in Santa Cruz. Life in California is pretty outdoorsy and if you are, you probably can't beat the west coast. You'll get a longer summer and a milder winter, and you're what most Americans consider a manageable drive from the heat of LA and southern California (5-6 hours on the fastest road). NYC - trips upstate are popular, and hitting the Hamptons / Long Island / Jersey shore in the summer.
Anyway those are my thoughts, off the top of my head.
Seattle, I have never been to. I know it rains, a lot!