You need to spec out your question much more for a meaningful answer.
In particular, unless you are dealing with a very large (many terabytes at least) amount of data, you'd be able to achieve your goals with either type of system without any significant trouble. Just pay attention to your schema / index design on a RDBMS and it'll be at least comparable, and at best blow the pants off of your NoSQL solution, especially if you do anything more complicated than key/value lookups.
To me, it'd boil down to: which do you understand better? I know PostgreSQL much better, so I'd use that, but your skills may differ...
--EDIT--
If all you're trying to do is store data, then just shove it in a text file or something. It's how you intend to retrieve / process it that it gets interesting...