For a long haul flights I think another consideration is if you want anything "extra" outside of the meal/drink service during flight. I find that flight attendants are much more generous with extra wine or snacks upon request for passengers seated in Delta Comfort. I have noticed FA's politely refusing a wine refill or snacks to main cabin passengers when not during meal service.
Plus A330 has some of the best delta comfort seats on all of delta. The 2 seat side is great! Even better if you can get the bulkhead.