I can’t vouch for any of the others but I am a big fan of Thousand Greens which has proven to be a great way to access private courses in the US. I have just come back from a 7-round, 6-day trip to New York and Massachusetts all of which are in the world top 100 or the 147 custodians lists.
It is Golf Club Atlas that has stimulated a curiosity in golf course architecture and having played a good few courses in the U.K., I was really keen to see some other architects’ work, such as Tillinghast and Raynor. Without Thousand Greens I doubt whether I could have put together a trip to see courses such as Quaker Ridge, Myopia, Eastward Ho! and Wykagyl as I cannot access such courses from my current network.
I have also found the community on TG to be great. I did have a couple of potential hosts ghosting me during the planning phase - and it did take a lot of work to arrange the trip - but the vast majority of hosts were extremely warm, generous, love their golf and I’ve made some great friendships. The spirit of TG is to ensure your host is not out of pocket - ie you cover the caddy fees where appropriate - but certainly not for them to make money. I struggled to make this happen as hosts either wouldn’t let me pay for their caddy or in some cases covered my guest fee.
The site itself is evolving and whilst some things could be improved I’d prefer it to remain a bit clunky and a hobby than it becoming slick but commercialised,