I mean, they are cheaper than Reiksguard, but not by much. Also, they are worse in every way.
I've included a couple of Empire Knight units alongside a Reiksguard unit in one of my armies, just to let Reiksguard boss around.
What I did not expect was Empire Knights sucking so much in comparison. They die to dogs, they die to marauders, they die to chaos chariots. Yeah, they can flank charge some poor sods, but who the hell can't? Seriously, why did they even bother with the inclusion of Empire Knights, when you can have Reiksguard who will win all of the engagements listed above?
And aren't Reiksguard supposed to be the Reikland's Knightly Order anyway?