Neither of these would be my first choice - but of the two of them, I'd much prefer WAW
I know DYTAM is liked by many, but I'm afraid I've always thought of it as one of the lighter and less standout songs on "BA". While it would undoubtedly give Carrie another radio hit, I think it would do little to enhance her reputation, or reinforce the impression of this album as a major step upwards for her. For that, I do think a stronger and more unusual song would be better.
Both songs are built around a similar theme - a woman's regret that new loves can't recapture the special emotions she felt in an earlier relationship she looks back on, but can't recapture. However, the regret is stronger and more deeply contrasted in WAW. In DYTAM, the main metaphor for the attraction of the past is that the new love tries to sing the same song, but always sounds a little off key. That is a good metaphor - but not as forceful or dramatic as the contrast between wine and whiskey. The latter, to me, sounds both more anguished and more mature.
I would compare WAW thematically with the RM duet. Both are mature, emotional songs. RM refers to an earlier stage in a powerful but jaded relationship, in which the couple are trying to get back to the passionate excitement they once knew. WAW refers to a stage where a passionate relationship has already ended, and the woman shows her pain in not being able to recapture, or match it. Both are big steps up for Carrie - the important difference being that WAW is Carrie's own song, and an example of her growing power as a songwriter.
I think WAW is a great album track - and it would have been one of my choices for a "new level" mid-era single release. Now though, I think the more pressing stylistic need is to go out on a high impact Country Rock single.