Hmmm both softwares are quite different.
If you want to focus only on iPhone/Android games, and publishing them NOW, I'd say go for Corona.
The main advantages are:
- Performance on broader range of devices: With HTML5 you'll be stuck with players that already have the latest Android or Apple update (iOS 5.0). This filters out lots of users that can't play your game because of framerate issues.
- Access to iOS/Android features: Accelerometer, GPS, In-app purchases, Gamecenter/Openfeint. Currently you can't access them in C2 - at least I haven't seem any tutorials, perhaps with Phonegap this can be achieved. I'm about to test the retina/normal graphic swap, but I'm quite sure I'm just get frustrated and forget about it :P
- Out of beta: Mostly stable software, with lots of code exchange and documentation. C2 is still in beta, and while everything is running smoothly and with uber-fast updates, you could be stuck with a problem or limitation until the devs can fix it.
Don't get me wrong, I love Construct and I'm sticking to it - even knowing a bit of LUA and Corona! The best option for you would be prototype the game on CClassic or C2, tweak and test it, and them port your final version to Corona for maximum compatibility and perfomance.