If Bandon Trails were the only course on the resort, I would have enjoyed my trip, but I wouldn't be planning any return trips in the near future. I enjoyed the course, but I too found the middle stretch to be a bit mundane (relative to the rest of the course and the resort.) #7 and #12 were the least interesting to me, and everything in between was okay but not spectacular.
If PD were the only course out there, I'd have still gone back the second time, and I'd still be up for a third. I will admit that both BD and PD got better the second trip, so BT may do the same. I'd still dedicate a day (36 holes) to each of the three courses, but my bonus golf (assuming they don't change the awesome policy!) will be at PD.
At the end of the day, if you took BT and put it in a remote location by itself, I couldn't see it having the same appeal as Sand Hills. I could see PD going solo if need be.