Studies show that you put your best 3 hitters in the 1, 2, and 4 spots, with the OBP guys in the #1 and #2 holes, and the SLG guy in the #4 hole. That said, who goes where doesn't make enough of a difference to worry about.
That being the case, Beni and Betts should be placed where they feel most comfortable. If it turns out that Beni does not perform well leading off, and I'm not saying that that is or will be the case, then Cora should put him back to batting second.