I am addicted to AgfaColor 100 and 400 - and certainly the Portra 160 is not out of the question for all my work. I *love* the stuff ... but there is probably something of pre-conditioning ... I've used these for a long time ... and I guess I understand them.
As far as transparency film ... I've made the photography of art work - for submission to Art Schools and Galleries - a side line. No one will be more critical of color, definition, etc., than the artists themselves. I personally would not even think of using anything but Agfachrome RSX100. That is one area where being a "perfectionist" is very nearly a critical requirement.