So I chose Unity, but my runner up was Corona. For iOS and Android games, Corona is certainly a solid choice. From what I gathered, 2D game development seemed more straightforward than on Unity. And it’s capable of great results — the polished Major Magnet for iOS was made with Corona and proves that point. But a few aspects helped push me to Unity:

• Corona is multiplatform, but only for mobile devices. No PC, Mac, or console support. Those platforms aren’t my priorities, particularly not immediately, but I want them to be options.
• Corona builds are made “in the cloud”. You can run your code on a simulator without building, but if you want to build, it has to happen via their online process. There’s a benefit: they update the SDK often, and you don’t have to worry about constantly downloading SDK updates. But if either you or they have network problems, you can’t build. And if the company ever goes out of business, effective immediately you can no longer make builds — unlikely, but still a risky position to be in.
• Corona requires a yearly fee to keep using it. The per-year fee is less than a similarly-featured Unity license, but the Unity license is permanent for that version of the software. If this works out for me, I intend to do this for at least a few years, so the larger up-front cost ends up being a better option.