Here are the terms and conditions for the NW discount certificates: https://www.e-rewards.com/northwest/nw_terms_50.jsp

In the past, they were a very good deal. Now, I notice that there are a myriad of blackout dates (including all Sundays). This would be a deal breaker for me but check when you want to travel and it might work out for you.

I almost always redeem for HiltonHhonors points. I stay at many Hilton Family hotels throughout the year, so I use the E-rewards redemption to top off my account. I would not redeem for Hilton points if I did not usually stay with them.