Why PPSSPP runs fast on decent hardware meanwhile other PSP emus are slow?

[DragonNeos]

I wanted Nezarn to give an answer since his response seemed like a typical wise-guy answer like "Since a program is coded in Java, it's obviously going to be slow..." If people are going to respond to questions like this, at least give evidence and details. A response like Nezarn's implies a lack of knowledge and may lead to others being misinformed about JPCSP/Java.