What is the difference between the PS1 and PSP versions of Tales of Eternia?

Just curious because I was wondering if the PSP version had any extra features (like advantages) over the original PS1 version as I started with the PSP version first so that I could see what the game was like.

However, while I do use the undub version, I don’t know why the official English dub was so questionable to begin with as I have heard reports that the US dub was so dub that it made newer players switch to the Japanese dub for those who know about the undub version, so I apologize if that part is not on topic, but I would like to know why the original USA version got such poor treatment.