Strictly from this reader's perspective, Nifty is the archive. I find it simple and easy to use and it's What's New page is a great way to easily keep up on the latest updates.
I like that it's such a comprehensive archive. I love that I can go to Nifty and find a story that I read in 1995 (yes, last century!). It's the first place I go to when I want to find a story I want to revisit. Sure there is crap there, but crap is in the eye of the beholder. If I were running Nifty and tried being gatekeeper on quality, about 95% of it wouldn't be posted. However, if I were running GA eFiction, about 70% of what's there wouldn't be allowed. Again, eye of the beholder.
Nifty's survived many years when other story sites have come and gone. For example, now that Archerland has closed, I was worried about what would happen to Jfinn's the Human Condition. Luckily, it's still on Nifty.
So to answer your question, I'd say Oui to posting on Nifty.
So basically, you want to use Nifty to gain readership, but as soon as you hit the big time, you'll leave?
Your questions kinda sound like some of the reasons Nifty has had to add all the fine print in their Terms of Service. If I were Nifty, I'd probably be miffed too with Authors requesting their stories being pulled. Or Authors posting some of their chapters on Nifty and posting the rest of them at another site.
It's been my experience that some authors can at times be sensitive & egotistical . As the Nifty archivist, that meant he was dealing with hundreds, if not thousands of them. Nifty's TOS are probably a response and a coping mechanism to reduce the amount of work he (they) had to do.
I think if you mentally commit to posting a story on Nifty, I think you should post it to completion on Nifty (whether or not you get hosted elsewhere in the interim).
Take Care®,
Vic