I've been covering South America for work for a bit so have done both recently - if a nightime flight where you'll sleep then I'd do the LA flight for sure. If daytime and I'm just going to chill and watch movies then DL as the food is better and service/refills/etc. are way more responsive. Don't worry about a switch to an LA 2/2/2 config...if that happens see if you can get swapped to a middle aisle, they're actually super comfortable to sleep in and nobody to step over if sititng in the middle set. When flying LA overnight I typically load up on food in the lounge and skip the onboard dinner and go right to sleep.