1964 works better with many games including Banjo-Kazooie and DK64 which have core problems on PJ64.
1964 is also faster than PJ64, has per-plugin settings (so you don't have to keep switching plugins), nice interface, uses all the same plugins as PJ64 uses and the same saves if renamed, has tons of frameskip-type options integrated into it, and has an option to change the RSP plugin in the config which is awesome. Overall, it's much easier to use than PJ64 is currently.
The emu isn't perfect, my niggle is that is uses too much CPU cycles and can crash on occaision especially if you have stuff going on in the background, but that is the only thing I can think of wrong with it. This will probably be improved for the final 1.0 release.
Other than that it needs a new hi-res XP icon for v1.0! Please
