Butter vs Oil and Dry Bread

The two whole-wheat breads I've made recently, both from Reinhart's Whole Grains book, were his Whole Wheat Anadama bread and Transitional Cinnamon Raisin Bread. Both breads had crumbs that were much dryer than I would like. I'm trying to figure out what I should have done differently. I make Reinhart's Oat Broom Bread frequently, with the same whole wheat flour, and that bread always turns out moist. Comparing the recipes I am wondering how much butter vs oil affects the moisture of bread. The Oat Broom bread calls for olive oil, which I use, but the other two breads call for either melted butter or oil. When I made them, I used melted butter both times. Could using butter make the bread more dry than using oil? I thought I would try using oil next time I make a whole wheat bread, but I figured I'd ask here first to see if anyone already knows. Thanks.