That's a humungous question. I've seen about a half dozen different shows and they've all been great. But it really depends on where you are. I've seen two different stagings - stadium shows that take about half a hockey rink, and shows put on in a travelling big top tent. I really prefer the tent shows because the venue is of limited size and thus there's an intimate feel to the whole affair. You feel like part of the show. As to which one in the tent? In my experience you can't go wrong. The Cirque du Soleil has a great look and feel and a particular way of staging the show that keeps you engaged from start to finish.
Live in Costa Rica, they brought Varekai, and now Amaluna is coming. Varekai was first I'd ever seen. Tent show. Wonderful.
The fun path is to find out for yourself. Make a point of seeing them all. Keep in mind that experience at each can be very different depending on where you're sitting. Being in the front row is fun, and you see details you miss from further back, but then you are prone to overlook the whole effect, which can also be spectacular. So maybe you should make a point of seeing them all more than once each. You have unlimited budget, right? As a general rule, I prefer the tent shows to arena shows because of the smaller venue. The fixed shows are in a category by themselves - the tech in some of them can't readily be duplicated in traveling shows.
I've been to three shows and the first was best (as most experiences are + plus we had VIP for that one and had more to drink). All of the shows I've seen really have a similar layout and method of showing the show. There is a rather simple hard to follow story line, with some sort of romance and there will a be joker/clown that fills the dead space. The base acrobatics and such are similar, but new acts are introduced. (Our last show had a new act that they did not use that night, so we watched the clown for an extra time...) When looking at Las Vegas I really think you have to tailor it to your interests. http://www.cirquedusoleil.com/en/destinations/las-vegas/home.aspx Do you like the Beatles or Michael Jackson, or would you rather see some extra skin? etc... Or the prices are $50 to $93 so you could decide on price.
In that case, here's my advice from February. No changes since then, though I continue to like the suggestion I made above of just trying them for yourself.
I've been to a few Cirque shows in Vegas and from best to worst: 1. "O" at Bellagio (Love the music) 2. KA at MGM Grand (Before they made changes to the show due to the incident) 3. LOVE at Mirage (If you're into Beatles then this would be for you) 4. Zarkana at Aria (It was just weird for me..) If you're into MJ music then ONE at Mandalay Bay would be for you. I heard good things about Mystere since it's the first Cirque show in Vegas (?). I also heard good things about La Reve at Wynn.