I would look for one of the following brands (keeping in mind that the lowly Atlas in great condition will be a better buy than a clapped out South Bend or any other once upon a time clapped out quality machine) condition is everything in used machinery, assuming you can find a machine well tooled and in decent shape I would look for one of the following brands preferably equipped with quick change gears (admittedly a personal preference) also the more heavily tooled at the time of purchase the better.
1) South Bend (Usually the name recognition alone drives higher prices; in good shape a very desirable machine that you usually pay a bit more to get)
2) Clausing (A fine machine with a strong following, also well supported)
3) Monarch (must have plenty of room likely phase conversion and
basic tooling, in decent shape a real fine machine)
4) Logan/Montgomery Ward (A more substantial machine than the Atlas/Craftsman that is actually still supported by the son of the founder!)
5) Sheldon (A name not known to many younger guys but a quality older brand that generally does not fetch as much due to lack of name recognition.
6) LeBlond ( I can only speak to the fact that the name is well known and generally known as a quality machine)
7) Atlas/Craftsman (when found in pristine shape not nearly as bad as some would lead you to believe; but they are a considerably lighter machine than the others on my list. Still a decent machine if you are not ham fisted and do not push the machine beyond it's limitations. additionally if you have strong monetary limitations a good entry level machine that should hold it's value with an abundance of parts both new and used readily available. A real weakness to these machines is the pot metal gears)
Some of it depends on how patient you are, what you can find close enough to drag home, how much you can afford, how well tooled and above everything else is condition! I always suggest taking a night class as a refresher at the local vo-tech before buying, doing this will help you figure out exactly what you need such as swing, distance between centers, minimum size of the thru hole at the headstock that you can live with not to mention you will know at least one guy that might have more knowledge of what is clapped out and wearing a shiny ebay paint job and what is actually a high quality machine that is still in it's work clothes with paint chips, stains etc. and how to sort out the two that might actually go with you to look at a prospective purchase. I hope this gives you some good ideas. BTW, check out this link.
http://www.lathes.co.uk/index.html