If you want a well rounded event with chances to demo skis, good weather, and bikinis - go to WF.
Surf Slam is a really good event, but consider that it takes place in a tiny little Oregon town with one bar, two restaurants, and one gas station. Weather may be good, it may be foggy, it will probably rain.
Don't get me wrong, I love the atmosphere and have gone every year since 2006 - when it was still the Blowsion Beach Party and not Surf Slam. You get to meet world class freeriders from around the world, ride with them, get drunk with them, and pretty much run into each other everywhere. Lots of entertainment on the beach and great riding.
Just be aware that the weather is hit-or-miss, probably 50 degrees at night and probably not over 75 during the day. The water will be 60 degrees if you're lucky. The surf will be below 12 ft if you're lucky.
Here's Surf Slam 2009: