The calibers are very different.
The 591 is based on the Lemania 8810 which is based itself on the Longines 990. The low power reserve is not a true problem since the double barrel improves the thrust.
The 777Q is a more contemporary caliber and I prefer it thanks to its better performances. There is a big gap in terms of power reserve.
When it comes to the watches... I prefer other options like the 5140 or the 5967...
Hope it helps.
Fx