Agreed, neither one of them are the most useful slings. The diamond sling is only good for long distance shots, where any other sling cannot reach, and this case is extremely rare. The bouncy sling – not sure about this one either. I cannot think of a particular scenario where this sling would come to mind as the most appropriate for the job, and I know what every level looks like.
Neither of the new slings have any special “power” ability like the specialty slings, and the golden sling. They do not hit any better than the original sling. Even the jingle sling, while it looks pretty, it does not have any special power behind it. The explosive ornaments make up for very little of what the specialty slings can do a whole lot better, and that is to smash.
Conclusion: For power shots, which is quite common in the Facebook app, the specialty slings “ice, wood, stone, and gold” slings are still the way to get more points. For levels with all ice or wood, use the ice or wood sling. For levels with a significant amount of stone, use stone sling. For levels with not much stone, but a combination of wood and ice, use golden sling.
Stone sling is still my favorite, because it is the most difficult to destroy, and also worth the most points. I find I can quite often gain more points using the stone sling than I can the gold sling. I’d say more than half the time, that’s the case, because there is almost always some stone that needs to be destroyed. That’s coming from someone who has spent a lot of time breaking down the game, and being as practical, methodical and analytical as possible.