Hi
, both of the factors you mention are certainly true, but it's a bit difficult to establish which has the greater influence over the fuel temp. Maybe some engineer can answer that.
Anyways, they put a temp. probe in the left tank because that's supposed to be the coldest, due to the smaller A Hyd System heat exchanger in it.
Not a bad question, and I also wonder if the temperature difference between the two main tanks can be really significant (personally don't think so).