Thank you ViniciusAlves.
We used robinshaafsma Unity extension, just fixed a couple of code lines throwing errors in 3.5 and replaced frameworks with the most recent one
We already published Pixel Volley with AppsoluteGames last year, they had contacted us and we decided to try since we don't know anyone at Apple and didn't know anything about how to market the app. The game got featured worldwide and went fairly well so for SteamBall we decided to go the same way.
It's hard to tell how much the feature depends on the publisher and how much on the game itself, maybe we would have been featured anyway if self-publishing, or maybe not, who knows? I have the impression that for us it played a good role, but this can be different for anyone