The Irix is still not available as far as I know,,, also try out the Zeiss ZM, there are threads on it here on NG and it's affordable on ebay co.uk
Samyang Et Al. build quality and sample variation is simply not ok for a Pro to risk,,,
The old 14 mm AF-D is build like a tank, metal casing with rear focus so no external parts moving actually more solid than an MF design, can be purchased second hand without any problems just make sure front and rear glass are pristine, it can/would show up in images if there are dirt or scratches.
BTW the 14mm hates shooting into the sun - unless you like colourful flares,,,