There is a white paper comparison between these 2 servers in the area of MMO gaming backend. http://www.smartfoxserver.com/downloads/sfs2x/documents/SFS2X_WP_PerformanceAndScalability.pdf
It doesn't seem there is a huge performance difference.
In addition, there are performance tests for Netty: http://www.jboss.org/netty/performance
So should I choose smart fox server or netty? There is always pros and cons depending on personal situations. Because my game is aiming to host up to a million client, smart fox server licenses maybe too expensive when you add it up. However, assuming I run game on Amazon cloud, even though the performance between the two is not that huge, the server usage saving when you deploy a game in such a scale could be significant.
On the one hand I do understand SFS is probably pretty optimized for gaming use, but Netty is open source and can have it's advantages. Netty has Apache 2 license, which means you can pretty much modify it and use it for your own commercial purposes. You can't modify SFS in anyway. Some features of SFS such as flooding, room management, and chatting are pretty much useless for a game of certain scale since you can write those lighting fast. What really is important is the socket engine performance. There are so many webpage MMO games on facebook, but almost none uses SFS. I think two reasons: one is license fee may add up, the other is you can't modify it for your own purposes. Zynga wouldn't use it since they want internal control over all their code and resources.
I don't really know which is the best choice. Help me decide.
