Tele Vue has a lot of information about the virtues of each eyepiece design on their website. Click on background tab for each eyepiece type.
E.g. For Delos,
http://www.televue.com/engine/TV3b_p...=183&Tab=_back
Eyepiece specifications at;
http://www.televue.com/engine/TV3b_page.asp?id=214
Scroll down for discontinued models.