I've never been across the Lewis and Clark bridge (at least via bike) so I don't hold any specific grudges against it. . . what is so bad about it?
For me, it's not just the fact that it's narrow, busy, and has a good climb on each side. It's the woodchips and other logging debris that litters the narrow shoulder. I got a flat on that bridge years ago because of the unavoidable debris. (Well, you could avoid it if you wanted to get into that busy lane...) I don't hear this complaint from STP riders, but I'm guessing that they get around to sweeping it right before the event.
Another thing to note: The Westport Ferry is a pretty cool experience. If you choose to go that route, make sure you check the schedule, as it only runs hourly.