I have been on both in F. Both are great. The 777 feels a bit more spacious than row 1 on the 777, but then you are further away from your travelling partner.
I believe the CX seat is the best F seat i have ever been on, the new LX F seat coming in second. Not been on the SQ 380 F yet.

I would take whatever CX flight has the better schedule / availablity.