I think that it goes without saying that recumbents and DFs have different speed profiles, and that the hillier the route, the more pronounced the difference is. So, if matching speeds with your DF-riding friends is a priority, it would be better to use a similar machine. For me, the comfort of my recumbents is still a higher priority, so I am willing to accomodate the differences. Sometimes that means riding alone, other times it means playing leapfrog all day, and sometimes it merely means working harder on the climbs and riding the brakes a lot everywhere else.