I've never flown a Tristar before, and the Diesel-Ten is my first jet experience, so I'll could be a bit biased here.
However, as Cessnapimp has said, Tristars are more advanced technologically, and they have RR-engines (my favourites). So in (my) technical standpoint, L1011 wins.
But I like DC-10 looks better than L1011, I never like L-1011's nose, it's one of the ugliest airplane nose I've ever seen (although I like the -500 series, but I always fond of all long-range, shorter bodied derivative, like the 747SP, A342 and Tristars-500). And the cockpit windows of the DC-10s, they're huge!!. I have talked to a DC-10 captain before, and he said that in terms of manuvering airplane in the ground, nothing beats the DC-10, mostly because of the huge cockpit windows. Not sure about the cabin windows in L1011s, but those in the DC-10s are the biggest among all the airplanes I've ever flown (compared to those tiny windows in Airbusess or new Boeings).
And the best thing about the DC-10 is the take-off. I heard ppl saying that take-offs in B752 is like inside a rocket, not sure abt that though since I've never flown on one, but I flew a 25 yrs old DC-10 last July and it still leaped to the sky effortlessly.
In all, my choice is still the DC-10, despite the early safety record