Upload & Sell: On
I do a lot of night shooting (auroras and such) and to me, the 17 TS-E's lack of vignetting wins the 2.8 aperture by a big margin, it's so nice to have an almost evenly lit night sky with wide open apertures, even if it's an f/4. My previous night lenses were Samyang 14, Zeiss F-Distagon 16/2.8, and Zeiss 21/2.8 but I am now preferring the slower f/4 TS-E for it's relative lack of vignetting. I will admit though, it's not good to have the moon or anything that bright in the frame with the 17 TS-E, it can flare like crazy.
I own personally today the 17 TS-E + 24 TS-E II and previously owned the 21ZE. I have had the 15 ZE on loan for testing, and my experience is that 24 TS-E II was the absolute king of uniform image quality, and the 17 TS-E and 15 ZE were equals in sharpness. I had the 15 ZE on loan before I finalized my purchase of the 17 TS-E to figure out which would suit me better and I figured I would get a lot more usage out of the TS-E, and haven't looked back since. Although the 15 ZE is definitely the coolest lens I've ever seen. I figure if Batman were a photographer, he'd have the Zeiss 15/2.8 Z*.