I flew last month: Atlanta to Tampa with a L-1011-250,
10 days later Miami-Atlanta with a 777 (both Delta).
Of course I preferred the Lockheed, simply because it is a plane not often seen these days, and here in Europe, you hardly see one!
But to be honest: The 777 was of course a lot newer: The interieur was more bright, the whole plane looked more fresh and clean from the inside.
The L-1011 was not very clean on my flight, and it seems Delta do not put much money in their Lockheeds to renovate them.
The colors of the interiuer looks like in the early eighties.
But they have these unique elevators (for the catering-"cars") in the Lockheed, really something special!
The space you have in your seat is in both types not too much, actually there is no differnce in seating-space between 777 and L1011.
The best thing in the 777 is this in-seat-video, thats really nice.
So, enjoy your flights,