Tricky one Joe.
Good to see there is some Pentax dealer competition in Oz after all.
I do own or have owned all those EPs, except the 8.5mm version in the XF (which has virtually nil field curvature, unlike the 12mm which has some acc to CN review).
The most comfortable of the three EPs is the XW-14. But the field curvature (FC) I cannot ignore on extended objects like globs and open clusters, and when searching for planetary nebs. Must admit that this is a bit disappointing because in every other respect this EP is tops. The T6 Nagler does have a flatter field and hence better sharpness across an even larger field. But the XW has less light scatter and better transmission, which is more important than FC IMO. The FC is not really an issue with most objects that only take up the central portion of the view: galaxies, DSOs and planets. But I am still learning this EP.
The 60 degree FOV of the XF is quite generous, not at all cramped, but 70
is nicer. Anything beyond that does not interest me all that much, especially when it comes at the expense of comfort as it does with the T6 (for me). The XF is more comfy than the T6 but less so than the XW. The adjustable eyecup of the XF does not extend far enough for me (but that is not unusual for me with this style EP).
The transmission and contrast of the 8.5mm XF compares very well with the 9mm HD ortho. The XF is a top EP price aside. And it's even better when you consider the price. They sell for 1/2 the price of the XW in the States and in Japan, so you might be able to negotiate on the price a bit.
Personally I would go with the 14mm Pentax XW or the 13mm Vixen LVW from
MyAstroshop.