Which Power supply is better for PC?

it depends on what you need it to do, both are 80+ Certified but the output ratings are vastly different. The 12v rail on the GS800 supplies a creditable 48 Amps where as the TX850 has a huge 70 Amps. If you don't need the superior 70A supply get the cheaper option. The GS is from the Gamer Series (hence the GS) and the TX is from the Enthusiast Series, both are good quality and excellent power delivery one has more Amps and the wattage is almost immaterial.