If I'd have to pick one, then I'd rather want a new Ninja Gaiden game than DOA6U. Its been a while since they released a NG game that was decent, plus, they could still do balance patches for 6 if they would really like to improve the game.
I would like a new Ninja Gaiden, though, I honestly don't have faith that KT would do it justice after all the hate that NG3 got... (NG3RE was a bit of an improvement). Making Nioh 2 the best they can seems to be the direction ATM.
@Force_of_Nature Possible to make Ninja Gaiden great again with Nioh 2 team behind it. On top of it, Sony has a lot of backup cash flowing out of their footsteps. Get Sony to co-publish it just like Nioh did, have the same team that did Nioh, and faith would be pretty pure.
With the success of both Nioh 1 and Nioh 2, I would be pretty optimistic with Ninja Gaiden done well with them behind it.
I would prefer for a Ninja Gaiden revival rather than new updated version of DOA6. Since the last time there was NG was Yaiba Ninja Gaiden Z (2014), I would prefer a new DOA title taking some ideas from their more profitable version like DOAVV.