I have the mats to max both, but I personally chose to prioritize maxing Wu Kong before I continue on Vivica.
My priority is Titans, since that’s ultimately where the best shot at good loot is. Knowing I’ll end up using Wu on every titan, it makes him a high priority.
I also have plenty of healers, though, and you may not. I already have Rigard, Melendor, Sabina, and Boldtusk all maxed. Vivica will ultimately be hugely helpful for raiding and PVE, but another healer isn’t itself as urgent of a priority for me.
So presuming your situation is similar to mine, I’d suggest Wu first. But you may have different considerations that your initial post didn’t include that might lean my opinion the other direction.