Just got back from a 4-day trip at Bandon. Played all 5 (6) courses. My preference is:
Bandon Dunes - most playable. If you're hitting the ball well, you'll score well. If you're hitting the ball poorly, you'll still be okay. Most importantly, I had the most fun playing this course. Actually, we had a blast.
Sheep Ranch - The views are incredible. Also had a lot of fun playing this course, but, there are definitely some holes that are pretty plain. The holes on the ocean though make up for this. Definitely worth playing. I actually played it twice, once in the morning, once in the afternoon. The wind picks up considerably in the afternoon, and 3 of the last 4 holes play straight into the wind.
Pacific Dunes / Bandon Trails (tie) - With Pac Dunes, you get incredible views. With Trails, you get a different set of incredible views. Both are great tests for your golf game. I didn't have as much playing these, as, if you're not hitting it great, these courses will punish you.
Old Mac - Nothing against Old Mac, I had fun playing it, just doesn't quite have the wow factor as the other courses. But, definitely worth playing if you have time.
I'll throw in Preserve, it's a ton of fun, and has some incredible views as well. If you're going to Bandon for a trip, Preserve is a great course to begin the trip on, get familiar with the speed of the greens, and how the greens break.
We stayed on-property, at the Lily Pond. It was perfect, and close to the Lodge. Any questions about food or lodging, I'd be more than happy to answer.