Do they accept opal? 

Also, is their market going to incorporate anon file transfer?

I'd really rather not compare apples to oranges. There are many marketplaces,
I personally believe every reputable coin should have a market of some kind. Opals Marketplace is apart of the development,
not just some place you can throw your coins. I'm sure it doesn't look like much right now,
but it will continue to see improvements. It is a prototype that future business will be able to use as a model for the online store front.

If your coming to compare features to features, be sure you more specific in your questions.
If you ask "Hows Opal different then (insert coin here)?" all I can say is if youtruly want to know,
then read the entire ANN and the entire ANN of the coin you wish to compare to.
I know this might take you a while, but you wouldn't be the first to do it.
After words you'd be more knowledgeable and informed.
Knowledge is power.
(I hope this didn't come off as aggressive)

We appreciate the question and welcome you to the community.