A friend on the i-Pentax Forum bought a Sony Full Frame Mirrorless
because his Pentax K-5 IIs + Lenses were causing him shoulder and neck
pain and he wanted a lighter gear.
Within a year he sold it and went back to the Pentax. Reason:-
a) He was not happy with the quality of the photos in RAW or JPEG
b) The body felt unbalanced with any lens beyond a 50mm.
c) The EVF was nowhere near to a Penta Prism.
Hope this helps.
Regards
Bipin
Thornhill Ontario