Actually, both options cost the same amount of echoes: 625 each. 50 Bazaar Permits at 12.5 echoes each and 250 Volumes of Collated Research at 2.5 echoes each. Though some may argue that one is easier to grind for than the other, there’s no basic monetary difference between the two. There’s also not really any different flavour text between the two, if anyone’s interested in that sort of thing.