It's a good film on its own merits, as opposed to being something that one should watch only out of curiosity or as a film buff. As to how it compares to Affair to Remember, well, I can now see why there are partisans for each. Love Affair manages to avoid some of the false steps that would later be made by Affair to Remember, but Love Affair also makes false steps that are uniquely its own.
Perhaps the greatest of these is in Terry's reäction when Michel (essentially the same character as Niccolo in the later film) begins to give his version of events when they did not meet at the appointed time. What he first tells her should at least disconcert her — in the later film, Terry momentarily thinks that she never actually had what she been hoping to recover — but in Love Affair Irene Dunne does nothing with that terrible moment.
In general, Dunne is not as compelling in the rôle of Terry as is Deborah Kerr. On the other hand, Boyer is, for the most part, more convincing as Michel than Cary Grant is as Niccolo.
The ship-board romance in the earlier movie is simply far too abbreviated to be particularly convincing (though we are mercifully spared the over-working of the intrusiveness of other passengers which characterizes the later film).
I was surprised to discover that Love Affair has as many musical numbers with children as does An Affair to Remember. But, in the earlier movie, these are fairly well handled, whereäs in the later film they are abominable. The children in Love Affair are average-to-cute, whereäs those in Affair to Remember are like something that Normal Rockwell would have painted — if he had actively hated children. And the song performed by the children in Love Affair (in this movie, the same song each time), though arguably sappy, none-the-less quite fits the story in a meaningful fashion.
Chris, who is a partisan for Love Affair (though appreciative of Affair to Remember) mentioned to me what he thought to be a problem with chapel scene in the later movie. I have to agree that the earlier film handles those specific aspects better. While I am (as long-standing readers will already know) an atheïst, these characters are not, and this interval in the chapel is where the two of them should recognize that they want a marriage that will be a sacred bond of love, rather than a convenient union with someone good and affluent. The later film fails to clearly convey this thought, basically because (as Chris would have it) it allows Terry's hat to displace the Virgin Mary; however, it does clearly convey that Niccolo is thinking that perhaps real happiness would entail marrying someone such as Terry. On the other hand, the chapel scene in the earlier film, like the ship-board romance, is far too abbreviated; the characters find themselves positioned as if being married one to another, but little more is conveyed than a sense that marriage between them is not unthinkable.
I was pleased to see that in Love Affair, as in Affair to Remember, the original fiancée and fiancé respective to the two principals are themselves depicted as good people. (We get that more clearly in Affair to Remember, but it is an element of Love Affair.) Any conflict or resolution that would come from having these secondary characters revealed as somehow deserving to be jilted would be altogether too trite and too pat. Nor would it be plausible that the heiress who wanted to provide for Michel/Niccolo and the businessman who wanted to provide for Terry could find happiness in each other.