I do like both.
Personally I would I like the Panthere as a thumb ring (so that there is a bit of space to go over my joint) and the clash as a middle or pointer finger ring.
Something that may bother me (and may bother you) is the amount of scratches that will eventually show up on the Panthere over time. We all know wear and tear happens for jewelry so it comes as no surprise to many of us. But it's just something to think about if you are okay with a piece that has a very smooth surface with no texture or design except the head.
If I had to choose between the 2, it would be the clash. It just goes better with my current jewelry collection and aesthetic. (none of which have rounded surfaces or any animal designs)
Regardless of what you decide to get, congratulations and Happy Birthday!