Any opinions on which i better generally?
Mike, I think it depends on what you’re measuring. 
If we’re judging by gem value, my order would probably be Yachts, UFOs, Unicorns, Nectar, Rockets — I’m always happy when I feel like I’m getting the best “bang for my buck.” That’s a win in my book.
But if we’re talking about how quickly they dump coins during a game, I’m going with Unicorns, especially in Mahjong. Those things can really crank out the coins. 
So I guess my answer is… Rockets may win the race, but Unicorns win the coin dump. 
Unicorns can dump out even faster on SparkPlug Poker at 500K bets. i used to do Mahjong. It was a 100% pure profit win, but too too dam long! The amount lost in Spark Plug Poker at 500K bets is very minimal compared to how fast you can empty those ponies!