You should be comparing both products in great detail. Ask to speak with technical staff on both ends (that's who will be supporting you), not just sales people. Speak with program owners & affiliates who have used both systems and get their feedback in private, away from the drama that comes with message boards.
If anyone would like a demo of NATS you can see it live at
http://www.democash.com There's no need to contact us for a demo, we have nothing to hide.
(please note that there is no ability to save changes in the demo)