[astro744]

Field stop diameters (mm): (listed in increasing true field for any given focal length of telescope).

Tele Vue Ethos, 100 deg., 21mm = 36.2mm
Tele Vue Panoptic 68 deg., 35mm = 38.7mm
Tele Vue Type 5 Nagler 82 deg., 31mm = 42mm
ES, 82 deg., 30 = 43mm
Tele Vue Plossl, 50 deg., 50m = 46mm
Tele Vue Panoptic 68 deg., 41mm = 46mm
Ricoh Pentax XW40-R, 70 deg., 40mm = 46.5mm

True Field of view (deg) = Field Stop Diameter (mm) x 57.3 / Telescope Focal Length (mm).

You gain only a few percent more true field going from 43mm to 46 or 46.5mm. However you do gain a significant increase in exit pupil which at f10 is important.

Exit Pupil = telescope aperture / magnification
also
Exit pupil = eyepiece focal length / telescope focal ratio

ES 30 gives 3mm exit pupil
Pan 41 gives 4.1mm exit pupil
Plossl 55 gives 5.5mm exit pupil

A larger exit pupil gives a brighter image including background sky which will affect contrast. I think on an f10 SCT there is merit in going from 30mm to 40mm not so much to gain a few percent of true field but more so to gain a boost in exit pupil (unless you are in the middle of the city and require maximum contrast).

Edit:
I use a Panoptic 41mm on my C9.25. I have not used a Pentax XW. The 41 Pan is a heavy eyepiece and benefits from a diagonal that is single piece construction (Tele Vue) to avoid possible unscrewing of the diagonal nosepiece (as found on other diagonals). However I keep my Tele Vue diagonal in my refractor kit and use a WO diagonal on my SCT. As long as I keep the eyepiece vertical it’s OK. A drop of glue on the diagonal nosepiece thread would fix this but I would rather not do this. As for the views I find the 41 Panoptic gives excellent low power views in my all of my telescopes ranging from refractors, Newtonians and SCT. I have the 50mm Plossl too but prefer the 68 deg field of the Pan although the Plossl gets used at times.