Has anyone had success using a medium flow nipple when feeding a breastfed baby a bottle of expressed milk? Or did it introduce any bottle preference over breast?

A while back, a LC told us to always use a slow flow nipple when feeding LO bottles of expressed milk. This morning I found out that he takes an hour to finish each bottle at daycare -- and now his ped wants his volume to increase too! I'm willing to try out a faster flow nipple to see if it helps speed things along, but I don't want to create any issues when he's feeding at the breast.