Best use of Delta miles is for domestic tickets with stop over. Last year I was able to get 6 tickets for 150K miles on a multi stop itiernary which was costing me 500$ per ticket. If I would have used them to fly to international then I doubt if I would have got anything more than coach to fly to Europe. International awards on DL at the low level are almost non existent (at least as a non elite I have never found any). The best program in my opinion is UA.