Guess it depends on your experiences, I worked on professionally, owned and operated a lot of light/med duty diesel engines.
I use to like the 7.3, they made me lots of money as a tech! But they are kinda turds and not as exceptional as everyone seems to think. Compared to the GM/Detroit 6.2/6.5 of the era the 7.3 were fantastic but I would have to give the Cummins the top spot of those 3.
The smaller CAT's aren't bad, but they are way overhyped to me, costly and a bit of a maintence hog. Cat rode its name and unfortunately some less then steller engines they made got ignored due to the name popularity IMO.
Having the opportunity to run almost identical trucks with different engines at the same time to the same mileage can give you a different perspective. Between 5 trucks we had a 5.9L common rail Cummins 230hp, a Cat 3116 215hp I believe, a '00 7.3L 235hp, a C7 230hp I belive, and a LB7 Duramax.
Out of all of them the Cummins was the most reliable and had the lowest operating cost, other people I knew that ran identical trucks backed up my experience with the Cummins.
Oh almost forgot about the IH 4700 I would occasionally use with the 444te, was slightly better then pickup 7.3 but still had gremlins that plagued it with power loss. And at 195hp it was already a bit of a dog.