You make it sound like choosing your transformation is like choosing the woman you'll marry.
And then if you don't like her the divorce papers and stuff will be a mess (The change coupon).
It's not very important to have transformation path, but, to not have it is kind of silly, since you have chosen not to have it, you are wasting the time you could be leveling your transformation up.
It takes TONS of time to level up your transformation (well now it doesn't have levels, but rather TP, but you know what I mean). If you go around without any transformation at all, you're just wasting away points that you could've had, but don't because you don't have transformation.
As for your question, any transformation is fine, just choose the one you like the most by Looks or, choose Paladin because it is superior in every way