Appcelerator Studio is the tool I have the most experience with I have been teaching it for years at various conferences and have my online course I did a couple years ago and am in the process of developing a more advanced course on the tool. It was perviously called Titanium Studio but since has been renamed to Appcelerator Studio.
The next one I just came across a couple weeks ago and I am still exploring but it looks very promising. It is called Fuse. One of the nice things about it is you can do your coding in your favorite text editor which I know every developer has their own favorite editor. They do have some tight integration with Sublime Text which is lucky for me since Sublime is my favorite text editor.
From what I can tell Fuse uses it’s own mark up language similar to Appcelerator but is extremely easy to pick up and use. I followed some of their YouTube videos and had an app and running in no time. One nice think I love is having it running on my mobile phone and when I make a change to the code it updates my phone automatically so I don’t have to publish it out to preview it on my phone.
Although you are working mostly with a web view again it still has it’s benefits because you can still access native mobile calls like using the devices camera as well as having a very similar look on all platforms. I like to be tool agnostic so on a project by project basis I would consider what tool might be best for each project.
Now I have not done a lot with Corona Labs but from what I know of them one of the biggest benefits they have is they more of a focus on gaming than Appcelerator does. I know you can still build games in Appcelerator but Corona seems to have more optimization for that. It is for sure something I want to check out more.