I used to supervise and assess MA dissertations on translation, which included a translation of a 5000 word text accompanied by a 5000 word commentary on the texts, the translation process etc.
One year nearly 20 years ago, there were two students from the same European country who were friends, always in each other's company and working together. I had taught them, but didn't supervise their dissertations. When I received their dissertations to assess, they were identically structured with each section and subsection of roughly the same length, but since they had translated different texts, the content was different.
However, I had these two commentaries to read and assess. At the time, there were no guidelines as to font to use etc. and of the two, one was in TNR, the other was in Arial or similar sans-serif font. I found the one in the sans-serif font took me half as long again to read as the one in TNR; I found it much more difficult to concentrate on. I had to take extra trouble to make sure I didn't mark that student down in relation to the other as it was the content that was to be assessed, not the presentation. Because of the extra effort I had to put in to reading it, my natural inclination would have led me to assume that the commentary was more pedestrian. It wasn't.
So my personal experience has always been that sans-serif fonts on paper are more effortful to read than serif fonts ... with standard fonts that is.
I made no comment to colleagues who gave their students handouts printed in 24 point Arial or Helvetica (depending on platform!).

Mr X