In a nutshell the A380 has higher spec and more features but because it used Emulators, Apps and OS that the company never worked on themselves without giving the cummunity who worked on the stuff any credit and not playing by the rules of the software agreements. The Homebrew Development Community that made the A320 what it is today, mostly do not wish to have anything to do with the A380 which would also inc the A320E which is same console minus wireless and G-sensor.
The A320 has a good base of support and still gets updates to Emulators and other stuff in the Community.
Emulation of GBA, GBC and GB are pretty solid on the A320, you can also install Dingux and Open Dingux that give the A320 a far greater libary or Emulators and Games.
As for NES again the A320 is good, SNES well its ok not perfect but if running at 400Mhz then most games run well, at a playable speed. Some problems may occur with glitches and speed problems with SFX Chip Games, and also Games that use transparency (Zelda Link to Past) will suffer a 10fps speed drop with transparency on, when off the frame rates are good but off course you will see missing sprites etc.
If you are after SNES then the Caanoo/Wiz are pretty good, but then again you can also go for the JXD S601 they are cheap and Andriod and should offer good Snes Emulation.