I find it depends on the number of subcommands and if those subcommands are clear. It's rather useful to have the options whittled down to just the ones you need if you know which subcommand you need but otherwise can be painful.
Grepping through a large list of options is also painful, seems ther needs to be a balance here.
But we are comparing the pain of searching vs the pain of having to re-run the help command for each possible subcommand, and parsing through all of that. Much easier to just have one command invocation and search through it.
There is a web analogy for this in how people organize FAQs. Some have a list of section links, and you have to click on a section to get the FAQs for that topic. Others just put everything on one giant page.
Here's the problem scenario with splitting things up into section pages: You think you see the appropriate section, but then you don't see your concern answered. There are two possibilities: either the organization was counter-intuitive and your concern was answered in one of the other sections, or your concern wasn't answered anywhere. And what's the only way to be sure? Visit every single section page and search through all of them.
Much, much less painful to just have it all on one page and search it.
Grepping through a large list of options is also painful, seems ther needs to be a balance here.