When I go traveling to a new city, one thing I want to do is to at least experience their public transit system. Does it feel convenient? Nice? Janky? It's one of the most defining things about being part of a city.
That said, Japanese trains are a huge relief after a few weeks in Thailand. In Bangkok, there are three main modes of transportation: Skytrain, a subway, and a ferry. Each is pretty nice but the three together aren't too expansive. The ferry is obviously restricted by where the water is, but not much is really right near the ferry (though there is a connection to the Skytrain). The ferries also stop by 10 PM every day, which is annoying. The Skytrain has three lines, one going north/west, one going south/east, and another to the airport and is generally pretty quick. It brings you to a lot of major destinations i.e. Siam, Weekend Market, Silom. The underground metro, which only has one line to my knowledge, is much slower but likely passes through more residential areas, and does connect with the sky train as well. The only issue is that the coverage by these three leave a lot to be desired, so many people still rely on taxis. So, if you live near the Skytrain, you're generally in good business in Bangkok.
When trying to go to another city, forget about trains even if there are trains. Most people I've talked to recommended taking buses, which are somehow faster than taking trains. And there might be one or two trains to a certain place per day.
In contrast, Japan's railways are as convenient as always... as long as you understand it. It's not hard getting lost in the Osaka or Tokyo metros, but once you understand them you can usually get from point A to B really painlessly. Getting between cities via the Shinkansen or any other train is painless. I'm staying in a small town called Minoh outside of Osaka city, and via train it's only 20 minutes getting in and out. The most surprising part is the transfer. You get off the train, you follow the crowd, and the train is there waiting to bring you to Minoh. And this train only has four stops: the transfer point and three stops in Minoh. They built an entire train line to service one town that is about 50 square kilometers. And the trains do tend to service middle-of-nowhere locations in Japan in general.
Shortfalls include service times. Last train is at 12/12:30 range. If you miss it, you're SOL. Taxis cost a fortune in Japan. The same trip that would cost maybe 90 baht in Bangkok costed 1400 yen last night. And this issue exists everywhere in Japan, from Tokyo to the Osaka to the Shinkansen. Bars close extremely late in Japan and in the past I've resorted to riding the very first train of the morning (5 am) to get home. If there was one train per hour per line from 1 am to 4 am, fine and perfect I'm down with that.
Some buses operate over night. The night bus (夜行バス) takes maybe 6 hours between Osaka and Tokyo and depending on which you take may stop every hour and a half for a pit stop, which sucks if you're trying to sleep.