SEA-JFK: Lie flat (767) out, C+ back (757) or C+ out (767) recliner F back (757)
Flying SEA-JFK, I can only get one direction in F and the other direction C+ within budget. I do not really count on upgrade on this route as DL Gold, but who knows.
Option 1. SEA-JFK on lie flat business 767, return JFK-SEA on 757 in C+.
Option 2. SEA-JFK on C+ 767, return on domestic 757 (recliner) F.
Same price.
Having guaranteed lie flat on 767 in one direction is great, but I still lean towards option 2, because C+ on 767 in very comfortable and there is bigger chance of upgrade on 767 (36 lie flat seats) compared to 757 (20 seats).