I wanted to discuss about this, since I think might interest various people. I was talking with a developer friend about the various differences (and pro / cons) of the various MMOs possibilities:

pure webgames (boutique games, etc)
PRO: easier to program than other system, usually programmed in php or other server-side languages, low bandwidth
CON: probably lacks of "features" like music, animations etc unless integrated with flash components

flash / social MMO
PRO: hm well I suppose the viral marketing, you can have all features of a downloadable (audio, anims, etc)
CON: usually you can't go fullscreen ? and limited 3d capabilities and framerate issues. I also heard it's very hard to debug/mantain (not sure though).

full client/server downloadable
PRO: You can go fullscreen and take full advantage of computer specs (no low framerate, full 3d, etc).
CON: it seems the less used by indies, not sure why? harder to program probably too

Personally I was thinking about the 3rd (client / server) because with python is really easy to do network code and is a language I love (as opposed to AS which I hate! lol), but I'm a total beginner and probably is a bad idea. I was recently intrigued by some php games, since probably is easier to make than a full downloadable one. Another solution could be to use Unity but I would have to learn it from zero...

Any suggestions are welcome, I want to hear what you think about those solutions or if you know of other ones!