The Seasonic is the superior power supply.
Here is a useful list to use when shopping
http://www.tomshardware.com/answers/id-1804779/power-supply-unit-tier-list.html
Tier one - The highest quality and most stable PSUs available on the hardware market today. Highly recommended for any situation
Antec
High Current Pro - 1200 watts
High Current Platinum series
Be Quiet Dark power pro P10 (Greater than 750 Watts)
Corsair
AX / AXi series (MK1 AX series is also an excellent choice)
AX1500i (MK3 AX platform, Titanium efficiency)
EVGA
Supernova G2
Supernova P2
Kingwin Lazer platinum series
PC Power & cooling Silencer series (Only above 610 Watts)
Seasonic
S / M12 II Bronze series (Includes EVO series)
Platinum series (Fanless or not)
X series
Super Flower
Leadex Gold series
Leadex Platinum series
XFX
Black edition series
XXX series