if you had a choice

Any chance you could modify you plans to do both? The areas are very different and both are very excellent. From Brookings, OR all the way up you can't go much wrong in OR. Newport is nice but the RV park mentioned above is VERY expensive compared to other options. Another post also mentions the Olympic Loop are in WA and it can take weeks to explore just that general area. You can also catch a ferry across the Strait to Victoria Island, Canada for a great day of exploration including the Gardens.
If I could only pick one for an entire season I think I would go nuts knowing there was soooooo much I was missing!