Exaggerating a bit? You should the number, you might be surprised of the little difference between the two.
Seeker-like bonuses like the ones in Kensai are biased toward larger crit ranges, for example.
The only difference the gap will be noticeable is because the swing rate of Grearsword horribly sucks. Fix that and you'll see much Greatswords.
So does faster swing rate. Are you complaining about Tempest I, Wind Stance and Zeal too?