Stats doesn't tell the whole story, many units are far better(JHI) or far worse(Varangians) than their numbers imply. The Lancers have armoured mounts, which only a preciously few units have in the game. If you really want to test their strength, run a few Custom Battles and compare them to other cavalry.

Also, when comparing to your Hospitallers, what exactly are you paying for those, in terms of recruitment + armor upgrade? I'm guessing the total cost is close to that of the Lancers.