I know that most of the websites aren't for free, so I'd like to choose wisely 1 or 2 of them that I know in advance will be worth paying for. Would you mind sharing your experiences with the websites I mentioned in the title, which ones are worth it, which ones are not, and maybe adding others that might have worked well for you?

I guess the most important things for me would be: i) a website with lots of online real users, and ii) a website with some people willing to come to Brussels. In that regard, I don't know, maybe there are also some websites from the US with 5 million users, and if 0.1% of the people are willing to travel, I'd end up with 5,000 active people willing to come, which could be better than any European website. If so, I'd also be open to subscribing to websites for people based in the US. Thanks a lot ;)