The trouble with OPRETURN is most people are using it with zero-cost coins, thus will almost certainly be pruned at some point since there's no value to the UTXO (FALSE RETURN burns it too).
To me the difference is OPPUSHDATA remains spendable, so you could attach a small amount of data to a bigger UTXO set, and most certainly it won't be pruned unless the data is top-heavy vs the coin amount. I think it's important to not burn coins with OPRETURN, or create a mess for the miners, so this seems preferable. Also, it allows the user the authority to spend the coin which effectively allows the data to be released. Thus user really has more full control of his own data. He's potentially given the power to erase his data. This also seems important over time. There may come a time when it's EXPECTED Nodes prune data routinely.
lastly, I'm guessing there will be some market solutions for data, offered by Node companies like TAAL and Mempool, via Teranode etc....
This should be where nChain begins making a decent living as I think they are far far far far ahead in the thinking here.
For now, I think the only permanence is timestamp + hash = a way to verify data hasn't been changed. But you must for now store the master copy data somewhere off chain, unless you wanna pay a lot of extra money atm.
Would you do me the honor of writing the definition for "Air" or "Aired" in SLictionary?
(don't forget a picture and an audio pronounciation!)
Well done definitions should earn the penny-spent (we charge to define to keep spam down) back after just two likes, as we pay 70% of all search fees to the WordSmith who gets a subsequent lightbulb-like-- forever (for as long as your definition is relevant to users)
We'll go live on SLictionary.com in July, but we're at MVP now. Between now and July we aim to make the site child-safe, yet allow adults to search for naughty words as well. Working on this concept (separation of proper-definition "church" and urban-words "state") so we can really be a proper dictionary that learns with cultural change and acceptances.