Yes the gefell has better resolution in the highs and midrange and tighter bass. I still prefer the sony on my voice solo but the gefell points with the better resolution. The files for the mix where recorded with less drive from the preamp to capture more the essence.
I already used a pultec pulgin on both to cut 100 and boost top. Also api eq plugin. But maybe I pushed to hard into the mixbus what seems like distortion.
Yes I used a deesser. Of course

deeser sometime even pushing the signal forward in a mix. The gefell takes deesser very good. On the sony not so good and the highend stays a little fizzy even with deesser. (Fabfilter deesser)
I really don't know which mix I like more. Maybe a for the more modern style and mix b for a little bit more natural, vintage (?) Style. A lot of modern rap like dababy are sounding a little bit cluttered to me. In my mind the sony is more of a one trick pony and the gefell is more of a workhorse. So I should keep the gefell I guess and think about if I need the sony.
Recorded some people on the gefell and it was at least ok. Don't know about the sony in that regard.
I did not add any stereo effects on the vocals or saturation beside of tape. To show more of the essence of the two mics. No fancy stuff just little reverb and delay.