Not sure what you're looking to do with the cakes, but they're not really good for throwing the way pies are. The cake portion just kind of crumbles--it doesn't really stick.
Cakes can be fun for stepping in if you're into feet or sitting on. But I don't recommend them for throwing. If you do use them for the things I mentioned, try to buy fresh ones. Stale cake and hard icing isn't worth the cheaper price.
Walmart cakes have been amazing for me, you can check some of my photos to see them in action. Just need to make sure you leave them out so the frosting doesn't harden up in the fridge
I've had mixed results with cakes. Yes, they tend to crumble more than anything, and the frosting is usually pretty skimpy. Tres leches work very well, however, and I think Sam's Club has large versions every so often. Just depends on how much $$$ you want to spend!
Sheet cake is good but yes it crumbles. Clean up is a bear. Also, check out Clutch mascot for Houston Rocket. He's always throwing sheet cakes (YouTube).
Love you, too
