EPD was the older version, more closely aligned with the EPR/EPN era of films. I used a lot of it back in the day, quite grainy especially in comparison to more modern films. Has that classic Ekatachrome Blues thing in open shade. E200 was an improvement from the E100s/sw era of films, and was more oriented towards pushing. Without pushing it was relatively flat and low color, improved contrast and color at one stop push.
EPD always looked good to me at a slight push of 1/3 or 2/3, back when I did my own E-6, the colors had more snap and the grain got nice and crispy. EPD also cross-processed excellently, my favorite for that technique, very 90's look. Used to do 1-2 100ft bulk a month.
Never really got into E200, had some bulk rolls sitting in the freezer and did a whole project a few years back, and thats when I found that I preferred it at a 1 stop push. Now the Fuji 400 speed chromes rock E200 world, have not tried the 400x yet but the I like 400f better than E200 pushed. Still, some of those 'overlooked' chrome films have a very unique 'look' to them that are challenging to get any other way, so if you come across a batch of EPD/E200 its fun to check it out.