I'm doing les 2 alpes or Tignes every year. Both are good but don't expect a Breck park.
Les 2 alpes has a better park, bigger and more features(with a big jump, not big air but still big). Tignes is smaller and doesn't have a big jump. I had a lot of fun at both mountains. The advantage of Tignes is that it's way less crowded. Dilemma between more features or more people...
Snow is usually like spring snow, soft but not too shitty. This year should be a bit worse than last year though, especially for the quantity as the glacier in Tignes has now a base of 98cm. Last's year base at the same period was more than 2 meters... But there is snow all the time so don't worry about it.
For the afternoon, both are dope. Mountain biking is getting better and better. Tignes has got a very nice bikepark for 2-3 years, and you're pretty much alone on the mountain. Once again Les 2 Alpes, more people on the slopes, but still nice bikepark. One of the best in the alpes. 
Tignes has a waterjump, which is really nice. There is a nice skatepark, tennis courts, trampolines,... Pretty much everything. 
For the nightlife, more people in les 2 Alpes, better atmosphere consequently. 
You'll have a great time on either mountains. If your level is very high in freestyle I'd go for 2 Alpes.
Can't compare to the others like Saas and everything, but consider it also. Summer is about sun, fun and that's it, so you'll have fun everywhere I think.