PE seats on the 787-9 are about the same as F seats on the new 737-Max as far as seat pitch and width. Neither is as comfortable as the older F seats on the A320s but they are what they are these days. What I can say is that, between a couple versions of the 777-200, the 777-300, and several versions of the 787-8/9, economy is brutal on all of them. Economy Plus legroom is okay but you're crammed in shoulder to shoulder with extremely tight aisles. So, if you have someone 6'4" on a 14 to 16 hour flight, I would go with PE in a heartbeat if it is affordable. The food is better than economy and the seat is fairly comfortable.

Note on bulkheads in PE. While they have extra legroom, I find the seats uncomfortable because the video screen is built into the seat and the enclosure protrudes right into the side of your knee. I'm 5'10 so at 6'4" its more likely going to hit him higher up on the side of the thigh, but it is a consideration. I had flown bulkhead on 5-6 PE flights before my last one, and I'm up in the air on what I'm going to do with my return flight this weekend. I have 22F, where the armrest will come down, whereas I had 22D the other day and with the tray table on the aisle side it couldn't go down. That helps tremendously when the person in the middle row has their seat back You can just swivel out with the armrest down.