The air conditioning levels have been mentioned many times, so there's clearly something to it, but I can't say I've ever noticed.
For years, we always ate at RFC on AK days because we're not keen on the other options there. Having tried Yak & Yeti in January, we'll probably be opting for that for the foreseeable future - not because it's better, but simply because it makes a change.
The portions at RFC are huge and it would be entirely possible to share entrees. It has always struck me as a bit on the expensive side compared with similar eateries. It doesn't necessarily seem that way when you look at the menu, but I guess a dollar here and there makes a difference to the final bill.
We've only eaten at the DTD location once (back in 2000). It's much busier than the AK one (we're talking long waits) and so, all things being equal, I'd recommend the AK one. As I've already said, it's the standout amongst poor competition there, IMHO, but there are plenty of other options at DTD. All that said, I'd go for whichever fits your itinerary best. Once you're inside, you could be forgiven for losing your bearings completely - they're virtually identical.