Distinction between a Kohen and a Nazir

The halachic distinction between a nazir and a Kohen is noteworthy. A nazir is forbidden to become tamei to anyone, including his close relatives, whereas a Kohen is permitted. Why is that?

The following explanation is brought in the name of the Avnei Neizer: The sanctity of a Kohen emanates from his ancestors. It is fitting therefore that he should be allowed to contaminate himself by involving himself in the burial of his close relatives, for it was them (his father) that brought about his kedushah. The kedushah of a nazir, on the other hand, he imposed upon himself, and it does not create any type of bond between him and his relatives.

The Beis Yisroel suggests an alternative explanation. The sanctity of a Kohen emanates from heaven, and there is no concern that by becoming tamei to his relatives that he will tarnish that kedushah. However, a nazir, where his sanctity was self-imposed, the Torah was concerned that contaminating himself in any manner, even to his relatives, could blemish his kedushah.