What's the difference between a public relay like Damus and a Paid Relay like Nostr.Wine,  Which should I use? and which should I donate to? 
If I post does it post to both relays? are relays essentially parallel instances? or individual networks?

So many questions so little do I know, how long can a note fit?
And If I post something here, is it reliably existing forever?  i.e I can publically start blogging and build my business / journalism ?  or are we still in beta state?
 

 From my basic knowledge they should be parallel, but a paid one will often, and should, provide other features other than just connecting and broadcasting, such as spam reduction.