I have both, and like them both equally. If you like 1 Million & Black XS, there is a good chance you will like both. Like most PR fragrances, they are very sweet and quite strong. Ultrared man is a bit more of a gouramond, where the Ultraviolet man is more of a lighter scent. Hard to pick a favorite between them - but I would say if you like sweet, chocolate, vanilla, I would recommend Ultrared man. If you like sweet and minty, you should go with Ultraviolet man.
I think Ultrared Man is closer to 1 Million and Black XS than Ultraviolet Man is, but that may be a reason to go with Ultraviolet Man - to avoid going with something too similar (but I don't think they smell alike by any means).
I suppose if I had to keep just one, I would go with Ultrared man.