Paddy has recently upgraded to the 17 Ethos and I think he sold his 17 Nagler and 28 WO UWAN to fund it. I am not sure if his Nag was a T4 or not, but when I lent him my 17 Ethos at Snake Valley back in March he had ordered one himself in a few days. Said in his 16" scope it was no contest.
The closest direct comparison I have done was a 13mm T6 Nag against a 13mm Ethos and again the Ethos won hands down. Stars were noticeable sharper, easier to get precise focus, better eyerelief and as for that big field!!
Malcolm