Over the shoulder or first person?

IMHO the OTS perspective is as good for aiming as FP and it does also provide some propioception useful for jumping, taking cover, activating switches, etc. It takes some pixels, of course you can't get something for nothing. But I consider OTS superior to FP in most cases.

I think there are more games that use FP than OTS, so probably the majority of the people prefer FP.

I also think it would be really nice if it was possible to customize it. The workload for such a feature should be minimal, simply moving the camera from the eyes to over the shoulder, although that could lead to paradoxes by comparison, which makes that option even more intriguing.