With regards to the tripod, you'll want to call in advance before you bring the tripod to one of the locations. If you google "stratosphere tripod", you'll read stories of people being denied entry with a tripod. As far a Paris, I understand that the observation deck is kind of small for a tripod.
Last time I was in Vegas was for SHOT Show last January. I was going to go to Ghost Bar at the Palms because I understand that they had one of the best skyline vantage points. But it pretty much rained all three nights I was there and I didn't feel like pano'ing in the rain.


