The DL B764s are used on LHR etc so I'm guessing their cabins are amongst the nicer ones they have. The 763s they used on ATL in the winter tended to have older cabins, no ptvs etc.
Believe the only difference is capacity.
B764 - 40/206 - 246
B763 - 26/200 - 226 & 36/172 - 208 (Majority have capacity for 208)