They are all good, although with DoneDeal you can say you want €x and someone will say I'll give you €y, which complicates things a bit. You can of course put your items on all of these sites, they are all free (but do remember to take the items down from all sites once they are sold off one).
But if you want to get rid of things quickly the 2 most important things are
(1) Good photographs - well lit, of the entire item. If it would be helpful to a prospective buyer then take a second or third picture from a different angle or as a close-up (if it wouldn't be helpful then don't bother)
(2) Accurate measurements - meaning height, width and depth.
Of course you should also give an accurate description with a bit of detail, so "Kitchen table and 4 chairs" rather than "Table and chairs", or "Three-seater sofa" rather than "Sofa". And be honest about the condition of the item too (it will be a huge waste of your time if people keep ringing you for details you could easily have put in the ad itself, or keep coming out to look at the item and then decide it wasn't what they thought it was and don't take it).
I got rid of a kitchen sink unit, a radiator, a bathroom suite, a back door and a window all in a few days while other similar items languished on the same site for weeks and I'm sure it was because I did the above. (In case you're wondering, the way to take a photograph of a window is to close the curtains and then photograph it from the outside).