USB power on the screen's is pathetic.
Recently flew a Cathay Pacific 777 which only had a USB port on the screen - charging my phone from 20% to 100% took almost 4 hours. Meanwhile on other aircraft with power sockets (and a fast charger) the speed is 50 minutes for the same charge even my laptop (not fast charging) is around 2.5 hours.
I haven't been on the new A321/A320 neo's yet but the old A320 trans tasman fleet had the same poor charging speed.