UltraHLE was the first and the best n64 emu. It had great graphics, good sound, fairly good compat(for the time), worked on slow computers. However, the authors never continued the development of the emu. According to them, they only wanted to prove that n64 emulation was possible, and they did it.
Corn is the one with the minimum requirements. Nemu has a high compat, but that's all(it seems that a new version of nemu is about to be released, after 2 years with no status update)
PJ64 is quite good, but requires a really powerful computer. A Pentium III 800, 128mb, Geforce is the minimum requirements.
Daedalus and Apollo are also good emus(Apollo's author, Azimer, recently left emulation scene). TRwin, TR64 seems to be on a "break" for almost an year, but they are quite good also.
After all, all of them have pros and con, and there is no one that plays everything or that can substitute all the others. You can't expect to find a ePSXe kind of n64 emu.