Nunu vs Panth

Why is it that Nunu can ult in a bush and you cannot see it at all until he unloads a fully charged ult on your face, but Pantheons ult is almost completely useless. You can see Panth coming from a mile away and have more than enough time to get out of the line of fire. Then you add in the fact that if you cast ANY spell in the bush you get revealed as if you weren't hiding, but Nunu stays hidden with his ult charging and by the time you realize it...you just got raped for 2k damage. I feel this needs to be addressed. Panths ult used to be awesome but now when I play him...I don't even use it. It takes too long to cast then even longer to land. Landing 1 inch from where you jump should not take the same amount of time as if you jumped to max range.