I have 2.00 D of astigmatism and having also read that many observers favour a dioptrix that is slightly over their prescription, I decided to purchase two: a 2.0 and a 2.25.
I am inclined, solely based on experience, to say I favour the 2.25. However, there are nights that I cannot tell the difference or feel the reverse is true. I only use them with tv delites
I find that the following factors most affect my findings; magnification (exit pupil size), how well dark adapted my eyes are, and tiredness.
I have been using them for months and with many variables to consider, I am still not sure.
With a widefield ep like the 31 Nagler, I believe it may be difficult to adjust the dioptrix to achieve pin sharp images right across the field at the same time. Having said that, I sometimes have a similar issue with glasses and I feel I have to roll my head slightly to focus on stars at the edge of field.
No science behind this, just my experience