Mark - Generally a Logan lathe is a better/stronger machine than the Atlas.
For one thing they utilize steel gears rather than zinc alloy. In fact years
ago I sold my old 10x24 Atlas and acquired my current 11x24 Logan for that
reason; and because it had a quick change and took 5C collets. However, based
on the very limited information you provided on the 'older' Logans and the fact
that you intend to work primarily with aluminum, the 12x24 Craftsman lathe may
be the better choice. I'm not sure what you meant by "collet type headstock" on
the Logans and you did not mention the size, ie. 10x24, etc. The 11 and 12"
machines are significantly better than the 10". Do the old Logans come with any
chucks or other tooling? What size/type spindle nose do they have? Can they
take 5C collets? Do any of them have a quick change gear box; and if not, are
the needed change gears included? I also suggest the overall condition of the
lathes, especailly the ways, should be a major consideration. Keep in mind
that repair parts and needed tooling can be quite expensive. IMHO to be worth
the money you quoted, all these machines should be in good condition.
Good luck, John M