The Talmud, in Berachot 11b, records a disagreement between Shemuel and the rabbinic majority regarding the beginning of the blessings that we say immediately before Shema in the evening and in the morning. According to Shemuel, these blessings should begin with the words "אהבה רבה" - "With abounding love," while the rabbinic majority says that they should begin with "אהבת עולם" - "With everlasting love." Different ways of relating to this disagreement and the adjacent Talmudic material have resulted in the primary Sepharadic practice being to begin with "אהבת עולם" in both the evening and the morning and the primary Ashkenazic practice being to begin with "אהבת עולם" in the evening and "אהבה רבה" in the morning, as recorded by the Shulchan Aruch and the Rama, respectively, in Orach Chayim 60:1.
What is behind this disagreement? Do Shemuel and the other rabbis simply represent a bifurcation of the tradition about this blessing, or did they disagree philosophically about the meaning we're meant to express?
Making the question a bit stronger, the Talmud quotes a baraita supporting Shemuel, saying "We do not say 'אהבת עולם,' but 'אהבה רבה.'" That means that already in the Mishnaic era, there must have been people using each of these phrases, such that someone felt the need to make a statement in support of one. Again, why? What meaning was this person choosing, and what was he rejecting?
I realize that the rabbinic majority cites Jeremiah 31:3, which includes their chosen phrase, as support, but the fact that a phrase appears somewhere in the Bible is only a pointer to a place to find a possible meaning, but not a meaning in and of itself.
I looked at the major commentaries printed on the page in the Talmud, at the Rosh and Rif and the major commentaries printed on their pages, and at the Maharsha, and none of them discuss the meaning behind these two alternate phrases.