Listen to Czarpy. It varies from game to game, but in FE4, for example, almost every unit who doesn't have a horse is kinda meh. Of course, this varies some based on whether you're going for a low turn-count or just looking for a unit which doesn't need much training, but the former tends to be the metric by which units are judged.
In fact, only two armor units I can think of, Oswin and Effie, are considered any good throughout the entire series. And for the latter, it's largely because you can give her a horse.