As far as Delta goes, I keep hearing two things about it. 1) that their elite program is amazing. 2) that its incredibly difficult to actually redeem the miles due to low availability.
Given #2, I don't forsee giving them a chance.
Unfortunately, we can't utilize Amex so we are missing out on Membership points. I will try it out though when a high sign on comes up. I read about transferring to Singapore and redeeming RT domestic 1st/business seats for 40K on United. That seems like a great redemption.