1.- AIR for Android. Pros: Developing is easy and cheap (I got the Flash license bought for some time). Cons: You have to download AIR when downloading the game.
Surely you nee AIR, but you could use the
captive runtime option to pack your app, so there is no need to install the AIR app from Adobe.
2.- HTML5 game for the web. Pros: Today it's ubiquitous. Cons: ASSETS Theft (not code). For a quick online game this would be great but I'm afraid someone will just download the whole stuff with all the assets (animations, SOUNDS, MUSIC, etc). They would be in low resolution but...
Also true for Flash, Silverlight, Unity and every other kind of client side online game. If you download a '.swf', you can simply extract all embedded symbols, MovieClip classes etc. Even decompile the code (Flash Decompiler Trillix). So there is nearly no way to protect your assets, only a way to make it "harder"
3.- Flash for the web. Pros. Developing is easy and cheap. Cons: Today, distributing a flash game is a pain, even more when the game is in Spanish.
Almost every Flash web game is free-to-play and uses advertising as business model. If you want to charge a onetime price for a single game you better use AIR and distribute your game as digital download. Via Steam Greenlight for example.
As alternative you need your own server infrastructure and design you game as free-to-play (without saving), and if the user want to save his game, he has to pay for a premium membership (Digital License). Payment Service could be Paypal or Amazon.