From FBE's unit guide:

Mounted nobles
Charge 6 Attack 4 Defence 2 Armour 3 Speed 9, 20, 22 Morale 8 Cost 350 Support cost 105

Available: Viking campaign.

Dismount: In a siege for dismounted nobles (infantry version)

Mounted nobles are elite, have a large shield and are impetuous. This unit is the Viking prototype of the later knight. Because they are only a prototype they are a bit weak so make sure to keep them far away from any of the anti cavalry units, otherwise go ahead and use them as you would knights.


Royal bodyguards
Charge 6 Attack 4 Defence 2 Armour 3 Speed 9, 20, 22 Morale 8 Cost 250 Support cost 62

Available: Viking campaign.

Dismount: In a siege for Royal bodyguards (infantry version)

Royal bodyguards are elite, have a large shield and are impetuous. There are just 20 men per unit, 21 if the unit has a member of the royal family in it. If mounted nobles are prototype knights then royal bodyguards are prototype royal knights. Once again because they are prototypes they are weaker than the medieval version so you need to be a bit more careful with them. Otherwise use them as you would royal knights.



... The stats are the same!