Answer: In the previous Halacha we have explained the law of a Kohen’s daughter who may not marry a regular, Jewish non-Kohen who possesses no Torah or fear of Heaven. We must now discuss our scenario: Must a Kohen seek to marry specifically another Kohen’s daughter or is there no reason to do so?
Indeed, Rashi (Yevamot 84b) states: “As long as a Kohen can find another Kohen’s daughter to marry, he should not marry a Yisrael’s daughter.” This means that if a Kohen has the opportunity to marry a Kohen’s daughter who is compatible to him, he should marry her as opposed to marrying the daughter of a Yisrael. The Ritba adds that although a Kohen is permitted to marry a Yisrael’s daughter, it is nevertheless especially worthy for him to marry another Kohen’s daughter.
The source for Rashi’s comment stems from the Gemara in Masechet Pesachim (49a). However, in this Gemara we find no reference to a Kohen marrying a Yisrael’s daughter, for the Gemara there discusses only a Kohen’s daughter marrying a Yisrael. Indeed, many great Poskim point out this perplexity and write that based on our version of the Gemara, there is no concern for a Kohen to marry the daughter of a Yisrael. Furthermore, Maran zt”l points out a logical difference between them, for regarding the marriage of a Kohen’s daughter to a Yisrael, it is unworthy for them to be married, for their children will be Yisraelim and not Kohanim. It is therefore important for the groom to be a Torah scholar. On the other hand, when a Kohen marries a Yisrael’s daughter, their children will likewise be Kohanim, for Kehuna status is determined by one’s paternal lineage and there is thus no reason for a Kohen to abstain from marrying a regular, worthy Jewish woman.
Nevertheless, the Talmud Yerushalmi writes that there is indeed reason for a Kohen to try and marry a woman from his own tribe, the holy descendants of Aharon. There are several other reasons for a Kohen to marry specifically another Kohen’s daughter. According to the letter of the law, however, when the bride and groom are both Mitzvah observant and follow in the Torah’s path, there is no concern thereof and they may marry each other and need not worry about any harm befalling them, for the holy Torah will protect them and ensure that their marriage will be successful.
Summary: A G-d-fearing Kohen who wishes to marry a worthy, Jewish woman who is not the daughter of a Kohen may do so and need not be concerned about this at all. Nevertheless, it is especially worthy for a Kohen to marry the daughter of another Kohen. However, the most important thing of all is observance of the Torah and Mitzvot and in the merit of the Torah, the couple will be able to build their home on the strong foundations of Torah and fear of heaven for many happy and healthy years.