[clemos]

NME is particularily good in building "Flash-like" applications, so mainly games.

I think Appcelerator is more adapted to applications that want to use native UIs elements (menus, buttons, layouts, etc).

Then you can still write an Appcelerator app using Haxe :) https://github.com/skial/haXe-titanium-desktop

I don't know how/if it's possible to mix both, for example embed a NME app inside an Appcelerator app (besides using UI.WebView and embed it as HTML...)