Having operated both the L1011 civvy and RAF, and the DC10 in both short range and long range pax and freight, I feel qualified to comment.
In short, the TriStar was a far nicer aircraft to operate and Caledonian found that it made lots of money for them. It only went out of service when Caledonian amalgamated and the new company wished to change their image.
However, its nemesis was it was far too complicated for its time. The DC10 was far simpler and frankly the better aircraft - I disliked the FE panel as it was dis-organised in comparison to the TriStar.
But behind the panel, the systems were robust and well designed. Technically, the TriStar having 4 hyd systems vs DC10 3 might have looked better but the Sioux City deal would have taken the 4th system out as well, had it been a TriStar. That DC10 crew were also exceptional when it came to that 'test'.
Maintenance is everything though. BA maintained their aircraft very well and they were very popular with both crews, cabin crew and passengers. It was simply the bean-counters that missed the clue-in-the-name. Once their error was discovered, BA attempted to buy them back, but the RAF had those bloody useless underfloor fuel tanks fitted. When they were full they put the aircraft beyond its bending moments. They could have kept a fully functioning freight compartment and got around the stupidity of loading baggage through 1L.
BA operated both types and it's interesting to note that the BA DC10s lasted a lot longer than my greatest love, the TriStar (especially the 500).
I enjoyed my time on the RAF TriStars and they were great aircraft, that said, they have been asked to go way beyond the original planned life, so I wonder how many of the problems were due to lack of investment in spares and so on, because the aircraft was always 'going to be replaced soon'.
Best of luck 216, I loved flying with you.