Moving thread to Battle Planning....
The stats for GK vs. TK appear to be the same (including exact same stats for charge, primary and secondary weapon) except for defense:
Code:
total armor skill shield
TK 16 7 5 4
GK 15 10 5 0
And the TK have more armor upgrades available to them. However it is not the full story, to simply say that TK have better defense. TK will generally have better defense in all modes (melee / AP-melee / ranged / AP-ranged). From the front, for un-upgraded units, the numbers are approximately:
TK = 16/13/11/8
GK = 15/10/10/5.
But from the sides, shield numbers get halved, yielding approximately:
TK = 14/11/9/8
GK = 15/10/10/5.
Finally from the back, shield and skill are eliminated, yielding approximately:
TK = 7/4/7/4
GK = 10/5/10/5.
So, GK would typically fare better in situations where flank and back attacks could be expected; whereas TK are clearly better in arrow-rich environments, and if you can keep the flanks and back protected.
There may also be a difference in fear factor and/or mount weight (affects charge) between TK and GK. (I do not know.)
All that said, unless someone could point out a tangible advantage (fear and/or mount weight) I would spend my money on the TK.