Empiro said:
The ruby rune greatsword is too good not to use. The damage penalty on horseback doesn't master because it does so much piercing damage. The long reach is really helpful too.
Damage done by the 2 handed Ruby Rune Sword on horseback: 49p (35% of 75p) swinging, 30p (35% of 46P) thrusting. Speed 95. Reach 158
Damage done by Ruby Rune Axe on horseback: 65p swinging, 20p thrusting. Speed 95. Reach 98.
So, a Ruby Rune Axe deals considerably more damage (16 more, to be exact) on horseback than a 2 handed ruby rune sword, although the 2 H sword has more reach. On top of that, you can use a shield, which will save your life several times.
PS. Basically all this makes a difference when fighting elite level troops (lower than that you are going to kill them with a single blow). You can kill elite troops probably with a single blow (with the ruby rune axe) or probably with two blows (with the 2 H ruby rune sword).