What is the difference between the two? Which one should i use?
Sorry for the late reply.
So, we’re in a bit of a crossroads at the moment, with 3 WP to Static plugins in development.
This is how I’m describing them on my new personal site:
Besides the main feature differences (deployment & workflow automation options), which one to use right now is really down to the state of development.
Static HTML Output has just had a lot of bugs fixed and is awaiting 2 last changes before I publish that to wordpress.org and it should be the most useful.
WP2Static (V7+) is gearing up to be the most powerful, with more Add-Ons and deployment options.
For today, I’d probably suggest to start with SimplerStatic to generate a ZIP and then manually deploy that to your preferred static site host while waiting for the next releases of WP2Static and Static HTML Output.