You can get the essential information from reading this article : http://ruwais.info/ruwais-markets/
Here are a few ideas about what you could discuss about the markets: shelves order, product display and variety, vegetable freshness, helping staff and cashiers, cleanliness, general convenience.
My opinion is that : Emirates market has much more variety of products -> but it is more crowded and the fresh meats finish fast.
I live closer to Abu Dhabi Market, but the main shopping is done by my wife where ever she wants.