Seems like the question really is- "What WAS the best lathe when they were new?".
Because used lathes are like used cars- no matter how good they were when they were new, every one is different, with different problems, when they are 40 or 50 years old.
And all of these lathes are pretty much that old.
I think a really interesting story to read is Joe Micheals account of his company buying, and having rebuilt, a 25" Leblond.
http://www.practicalmachinist.com/vb/general-archive/leblond-heavy-duty-engine-lathe-79331/
The original lathe was a great machine- but this was 50 years ago, and a lotta miles under the bridge. Joe paid to have it modernized and rebuilt, and it ended up costing $55,000 or so, and that was in 2004. Factor in inflation, and the fact that shops capable of this level of rebuild are far fewer now than a mere 8 years ago, and I think you would realistically be talking more like $75k now.
Yancey, the shop in Portland that did Joe's lathe, is gone.
Now, admittedly, they had it converted to an infinitely variable speed AC drive, with DRO, but with today's materials, thats not a luxury, its a very handy thing to have done.
There are a fewer and fewer good old lathes out there- many of these machines have been out of production since 1970 or so.
I am not saying there are NO good ones left- but most will require some degree of rebuilding, and you need to account for that when buying.
Just like when I buy really cheap used cars, I figure an extra grand for all new tires (they always need em) a new battery, belts, a tuneup, and the misc thing that will go in the first month- usually the starter or alternator. When machines get old, people scrimp on maintenance, and the new buyer always gets stuck with it.