I was able to rent the Zeiss 15mm and borrow (CPS) the TS-e 17mm
Both are beautifull, super-sharp/IQ, heavy and MF only - but the TS-e is more versatile.
the 17mm will allow you to stich shots to get as wide as a 11mm lens, but you will need a tripod, so the 15 wins in FOV.
The rest you know - price.
If I could afford it, I would get both, but right now I rather wait to see what Canon is going to do (or not) regarding the 14-24 rumour.
If you already used both, and liked either, then there is wrong way to go, considering you being a generalist.