Increased resolution, faster performance, trophy support.
All 2D artwork in every title gets the upscaling treatment - there's nothing that can be done about that, and it can look pretty ropey. However, the 3D elements are substantially improved and do get a resolution increase.
[...]
In effect, we're looking at around 4x the pixel count - possibly higher, depending on the title. Texture filtering also looks improved, but on close inspection we think that the increased quality is probably down to the extra resolution alone.
[...]
The emulator is clearly running these games more smoothly, with Jedi Starfighter hitting 60fps while the game running on PS2 hardware has nothing like that level of output.




http://www.eurogamer.net/articles/digit ... -emulation