I don't have any direct experience with either of these tents, I just mention vague notions I seem to recall from reading reviews. (Take my comments with a grain of salt)

Yes I think you bought too much tent if you got an Unna for 3-season use. The Rogen is a 2-person tent... the unna is a 1-person tent. What do you want? I seem to recall some pretty positive comments about the Ahkto... which is also a 1-person tent... it seems more comparable to an Unna