I would be a 2xJ person too. Bearing in mind that this is a honeymoon trip, though, and that therefore you presumably want it to be somewhat "special", my answer would probably depend on your circumstances.

If neither of you normally flies in C or higher, C would have enough of a "wow" factor when compared to economy to make it somewhat special. If you both regularly fly C, then it would probably make sense to fly F this time, even though, as Southlondonbonviveur says, the differential between J and F is not quite so big.

In addition, there is always the risk that you end up with a not so good crew, which would significantly affect the F experience, especially if you have built up your expectation and invested a lot emotionally in it and therefore are more at risk of disappointment. Not so much of an issue if one flies regularly but more problematic if it is an exceptional trip. With 2 C class trips, the expectation will be a little lower and, even if things are not perfect, at least there will be another trip to redeem the first one.