The form
When the best option is not available, any other options are basically the same, any of them is fine.
When choosing the next best option, the second best.
Emphasizes regret over a concession slightly more than (이)라도, however they are in many cases interchangeable with little change in meaning. (이)나마/(으)나마 is not necessarily a second-best choice but rather just the choice that is available.