I Don't see a difference actually!
There isn't really a difference, you can just take DOF Screenshots that are bigger than the resolution of your monitor
Like say you have a monitor with 1024x768 resolution but you can't make Blockland go to any higher resolutions, you can use the Megashot feature to do so, and once you've set the Megashot factor and taken the DOF Screenshot, you'll have a DOF Screenshot bigger than the resolution you were using when you took that screenshot