NATS beats the hell out of a single processor solution by a good 20%, thanks solely to cascading. The stats are far superior than any ipsp's stats, giving affiliates campaigns and tracking tools. And thats not even taking into account other back-end superior features like geotargeted billing and instantly being able to add/swap/remove billers from cascades.

But really, it comes down to money. After moving to NATS, HunkMoney has seen an amazing 300% increase in affiliate payouts.