This often asked question is quite irrelevant, as different design's performance varies with different telescopes. Different eyepiece designs have various characteristics. For example, and expensive widefield design is not required for planetary viewing, where the only important thing is maximum contrast. A Plossl or Orthoscopic would probably be best, but almost all design s are good performers on-axis for any f/ratio. Telescopes with F/ratios>10 are quite tolerant of simple low element eyepieces up to 55 deg. A.F., but telescopes <6 are a different matter. Off-axis performance requires powerful correction to properly image the highly convergent beam. Each eyepiece and telescope performs as a system, and their image can only be evaluated as much.