I've always sold all of my minifigures opened packet, taking a photo of the un-assembled figure with accessories / stand / leaflat / bag in a sealed plastic bag. The price you will get compared to a sealed minifigure packet will be less, however for most newer series I haven't noticed a substantial difference in prices. For the early minifigure series there is a greater difference in price.
Opening the packet also eliminates the time needed for smoothing (if like me and are rubbish at it) and also confirms to the buyer they are getting what you are advertising.
There is a risk that if you don't open the packet and the buyer returns the item, he can just returns another undesirable minifigure from the series, you will not be able to win the case saying you smooshed the packet and received something else.
One word of advice, some will say that once the plastic bag packet has been opened it is no longer considered "new" condition, and you need to list any opened bags as used on eBay, however I have never had anyone complain about this, but it should be kept in mind.