I prefer the 788/789 as the PE is a 2-3-2 arrangement, where on the 77W/77L DreamCabin (refurbished) the PE is a 2-4-2 arrangement.

I do not like middle seats, so there is a greater chance of aisle or window seats on the 787s compared to the 777s PE cabins.

Note that despite the 38" pitch, if you are in a non-bulkhead row in PE, when the passenger in front of you reclines they will intrude in your personal space. It becomes difficult to use a personal screen (tablet or laptop) and the seatback screen is annoyingly close to you (unless you also choose maximum recline). There is enough legroom, though.

The downside of the bulkhead in PE is the tables in the fixed armrest. I don't recall if the entertainment screen is in the armrest or attached to the bulkhead, but neither is at an optimum distance (armrest is too close, bulkhead is too far).

I am not one that finds the 787 aircraft to be more refreshing due to the humidity/cabin pressure, and a good pair of noise cancelling headphones eliminates the reduced noise benefit. If you have good seats (not middle seats) on the 777, I would stick with it unless you find the arguments posted above compelling.