would choose nats from what Ive read. mpa still carries a bad name to some and when you're looking for new affiliates I would think it would help. Some programs are pushing the "we use nats so we can't shave" sales point. Good for people like me with little shave trust (especially with all the insane payouts some programs have).
Just my thoughts.. I've never used either, just read too much.
- kero