The seats on the 450 are narrow and upright, and quite hard, and so some people like them, and other hate them. Most of the 377s have a mix of narrow (5-across) and wide (4-across) seating, with the former in the inner 2 carriages of each 4 carriage unit. The 444s, should you get one, have rather comfortable 4-across seating.

However, outside of peak hours, you're unlikely to find yourself cramped in.