Nvidia DSR vs Custom Resolution

[Blackstrider]

Okay, so I have a 65 Inch HD TV @ 1080p 60hz that i have my gamining PC hooked up to. I know Nvidia now has this thing called DSR that you can use to set higher resolutions on a TV or monitor that dosent natively support them. Ever since I have used custom resolutions via the Nvidia control panel. Currently I have custom resolution of 1920x1200, 2560x1440 and 2560x1600. My question is just what is the difference and benefits of using DSR over settingmy own custom resolutions? Does DSR offer better performance and better visual fidelity? Does it use less resources/energy from my GPU? I just cant wrap my head around the relevance of DSR vs setting your own resolutions manually....

Help?

Intel i7-4790K @4.0 Ghz
EVGA Nvidia GTX Titan X SC
2TB EVO 850 SSD
Silverstone 600w Gold Cert PSU