the one thing that is important with the pounce is that you must get that chalk flowing into the fabric "terry cloth" on the bottom. So leave the cover on, put it in a plastic ziploc (which i actually store my pounce in so no waste) and bang it on the counter several times until you see chalk puffing out of the cover.
The take it out of the bag, take the cover off, and wipe it over your stencil which is placed appropriately on the quilt.
The advantage to the pounce is that it is very quick and easy to see. The pens can work great but they take time. Again, it all depends on your needs. You can only use pounce with a stencil, as far as I know. so if you see a pattern in a book or design something yourself, you have to cut a stencil to use it. That is not the case with marking pens and pencils. So it all depends upon what you have to work with.