you should use userscripts for the reasons I said plus:
- I can easily turn each one off and on without leaving the page I'm on
- I can modify it easily to suit myself better
- tampermonkey provides a whole lot of very nice settings, and allows YOU to write scripts with ES6 or CoffeeScript even if the browser alone doesn't support what you're doing
I'm unsure if any of the other extensions do the same things in the last bullet
which one is "more user-friendly" is very subjective. both adding and removing userscripts is more convenient than adding or removing extensions, at least in chrome
I mentioned before that you wouldn't have to package different versions for different browsers, but the real advantage there is that users don't have to wait for you to do so to use your script in a browser that you didn't prioritize. tampermonkey alone supports chrome, firefox, opera, and safari. other browsers that you might not have even heard of probably have their own userscript extensions
your second bullet is kinda meaningless, because most users who are interested in this kind of thing probably already have a userscript extension installed, since literally nobody but you has made actual extensions for the blockland forum
and safety, too, is meaningless. I doubt they will check for the kinds of things that matter. sending the user's session ID or some of their PMs to your own server could easily be disguised as legitimate collection of statistics to the people who check extensions, and have no specific experience with the blockland forum
in fact, tampermonkey has safety settings that would let you prevent any userscript from operating on login pages and things like that, which isn't a choice I get with chrome extensions