FA31 f1.8 Ltd vs FA35 f2

Dear fellow Pentaxians

I have the Pentax K7, the FA32 F2 (and the FA*28-70, DA12-24, DA16-45, SP90di FA50 1.4, M50 1.2, M50 1.2 etc etc). I shoot primarily portraits in available light and secondarily landscapes. Although I manual focus when possible, on many occassions AF is the only option or I loose the portraiture shot. Thus, good AF is low ambient light is an important consideration.

I am asking people who own and have owned both the FA35 and the FA31, what benefits the FA31 Ltd provides from optical and practical perspectives for portraiture and landscape photography. I will appreciate this advise before I buy the FA31 Ltd.

Cheers
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KNL