I think if you have the budget, go with bubba cups. Not only do they keep things cool for longer, but they also last forever so your guests will have them for years to come.
Another good option is tervis cups. I have a bottle from them and surprisingly it keeps my water quite cool during hot yoga (now this is super hot, dripping sweat in 30 seconds yoga). I'm not sure how the prices compare to bubba's. They're not as good insulators as Bubba's, but if they're cheaper I would certainly consider them. Last time I heard you can get 4 in one pack, which makes it more economical. They also have tons of fun designs
I just got one of those double wall cups from starbucks from Christmas. I love it, but they hold the temperature of the drinks for far less amount of time than the two above. If I was a guest and got a double walled cup i'd be stoked, but i'd have to drink faster . It still beats the small plastic cups you get from the bar and that's the whole point of the OOT cups. Also, out of the 3 I mentioned you can find them for cheaper and they're probably the easiest to carry down there.
I really think it comes down to your budget and your "must haves" for the cups. Whichever one you choose I'm sure your guests will be thankful and will be happy to use them . I know I would be!