An excerpt of the interview can be found below, and you can read the rest here.
“I have argued that to contemporary readers it would have looked more like good historiography than the Synoptics, because it is remarkably precise about chronology and geography, as good history was supposed to be. We always know where Jesus is, sometimes very precisely indeed (e.g. Solomon’s Portico in the Temple) and, within a few months, at what time events occur (because of the sequence of Jewish feasts that is carefully marked).
I find these aspects of John convincing as historically accurate, and where there is conflict (not often) I would prefer John to Mark, whose chronological and geographical scheme is quite simplified and artificial. (Mark has only one visit to Jerusalem and so he has to put into that visit all the traditions he knew as localized in Jerusalem. John’s several visits, with the Temple incident at the beginning, are more plausible.)
….Until the early 19th century, [John] was accepted as an eyewitness account, more valuable as history therefore than Mark and Luke. Schleiermacher still thought it the best historical source for Jesus. Then the idea that Mark was the first Gospel (which no one thought until the 19th century) became popular (and, I think, correct). The denigration of John as history in the 19th century had a lot to do with the desire by the major German scholars to find a historical Jesus who was not supernatural and not the Christ of the church’s dogma. So they imagined Mark to be portraying a purely human Jesus. Of course, they were wrong. Mark has a very high Christology, as is now widely recognized. They also thought John used all three Synoptic Gospels and just made up what he added to them. Few people think this now.”