slutide If I had to chose night or day, I'd do C+ for the night flight as I think the combo of extra recline and extra legroom does make for a bit better sleep.

I also like being near the front for getting into the passport/customs queue faster (though that can be useful at ATL as well). Do you have a connection out of ATL on the return? That could matter.

Included in the recline issue is my preference to not sit in the last row of C+ is possible so as not to cram the person behind, nor be quite as likely to be jostled if the person behind also has the extra 3" of space.

Recent experiences by me and a few others on different A330 flights we all noticed that the C+ part of the fwd Y cabin was warm. If that bothers you for sleeping (it did me) weigh that towards day flight for C+.