Im new to tanking aswell! I felt the same way.

In my opinion you need to level both and decide whats easiest for you.

I went with GLD until lvl 45 because everyone said it was easier but from my exprience war is easier(idk may change after 50) and more enjoyable tanking experience.

I leveled both to 40 before finally making my decision on which one to level to 60.