All DL 747/777/767/A330 a/c are the lie flat seats in J with direct aisle access. I'll take this over a middle seat (as available on on some UA a/c) anytime. The 763's used SEA-LHR are 1-2-1 and the middle two seats are good for companions traveling together.

The VS J product is known for being very good, although I know some who do not like their herringbone design.

Also, it may be cheaper if you fly SFO-LHR and CDG-SFO on the return; just an option to look into.