You can check it by yourself for example at seatguru or here:
Thai Airways International Seat Configuration Overview
Seating configuration in 77W is 1-2-1. Wheras upperdeck in 747 is 2-2. So you have to climb over your neighbour if you like to sit at the window. Wheras in 77W you have direct aisle access. Furthermore the hard product itself is much more modern.