For your money, with all things comparable, Voodoo Fest makes more sense. First, its $100 tickets for the entire weekend (3 days), in-and-out entry, whereas Vegoose is $150 GA BASE PRICE (2 days, no in-and-out entry; $80 for one-day) plus if you want to go see Vegoose at Night shows (like the Shins, Umphreys McGee at Vegas clubs like the Joint and House of Blues), those cost extra and you MUST buy a 2-day pass for it. Flights are actually around the same: about $200-$250 per person roundtrip to fly to Vegas and New Orleans. Hotels would be cheaper in N.O., as someone pointed out, and they could probably use the money more than Vegas.
I went through this same debate with my friend, who actually lives in Vegas. Because of that, I wouldn'tve had to worry about paying for a hotel there. BUT even with that, we found it was better to go to New Orleans, because 3 of our favorite bands (rage, pumpkins and Coheed and Cambria) are playing in New Orleans, so the $100 more than makes sense for us. This is just my opinion, you have to take into consideration the line-up. I know not everyone loves Coheed or the Pumpkins as much as I do, and the Vegoose line-up is very good: The Stooges, Queens of the Stone Age, Muse, plus Rage of course. And Vegas is a great town, but it is the weekend, the Strip will be packed and it will cost you a fortune to stay there for a weekend. In the end you have to judge the overall line-up quality and the prices of flights, hotels and tickets and decide which makes more sense for your money. I've never been to New Orleans, it will cost more to go there in my case, but I can still see all three bands I want to see by Saturday night, can fly back Sunday to DC and only miss one day of work.
P.S. The Strip Clubs in Vegas are great. Hit up Little Darlings if you there.