A absolutely massive difference, over 4 times the yield is possible plus better penetration of light in to the canopy. Also you will be able to use a larger space usually 1.2m square (4ft x4ft) with 650w.
Just make sure you have the height space to be able to hang the light slightly higher as normally with that powerful of light you need between 12-21 inches between the plants and the light depending if it is a LED or a hps.
Hope this helps pal👍