The "Daddario EXL150" 12 string electric guitar string set in nickel plated steel, these were supplied from the factory with my Danelectro DC59 twelve string, they sounded great and the factory setup, (was probably the best I have had on any new guitar !!) so I was happy to find the Daddario strings are cheap and readily available.
The set are made up with plain and round wound strings, gauges are 010/010 - 013/013 - 008/017 - 012/w026 - 018/w036 - w026/w046.
These are fairly "bright" sounding strings when new, I find they take a couple of days to stretch in and for the sound to dull a little, after that they sound great - clean, clear and stable, with the little Danelectro they give that classic 12 string jangle, full, crisp and articulate.
I use Elixir nano webs on all my six string electrics so I'm used to strings lasting a long time, the Daddario are obviously not in the same league but they do last quite a long time and certainly for the price they are quite brilliant.
I would find it hard to pay three or four times as much for the equivalent set of Elixirs when these perform so well, I think the only reason I would try an alternative is maybe to try a set of flat wounds some time for a real vintage tone but until them I'm more than happy to stick with the Daddario's.