We agree with wild1s, we were offered twice but only took up on the 1,and was kind of quite at Pearl, we like the Temptation wildness and partying, but never been to RM Desire, that might be interesting.
Since my wife and I enjoy both TTR and Desire, and regularly stay at both, we let the front counter know when we check-in that we would gladly take the bump should the issue arise. Visiting Desire for the cost of TTR doesn't get any better, and since most of the cheap rooms sell first, you are likely to end up in a mid level room as we have in the past. Now, this works for us because we fit the target audience, but it is not for everyone. My suggestion is if you have never been, take the bump. I can't imagine anyone ever regretting it even if they continue to choose TTR in the future. It is a wonderful and accepting atmosphere that simply cannot be matched anywhere else in the world.
We also like both TTR and Pearl for different reasons and we do try to split the vacation, although not equally due to the price differential. In July, as members, we are paying $1561 for 4 nights at Pearl in a Jr Suite (have to go there, our friends are tying the knot on the beach July 3rd) then we do 9 nights at TTR for $1260. If we run into or make new friends at TTR, we stay the duration, but we have been offered the option to transfer back to Desire due to full occupancy twice.
Due to the cost of Desire it is unlikely that we would try it at this time unless it was a bump from TTR. And of course we all know how much we like to "bump" at TTR...the grind is pretty good as well!