Only real advantage is being able to see how much
juice is in the cup, and oooooooooooo.......cool, it glows orange on a dry burn

OK, to be fair, it does help a little in changing flavors really quickly. A quick blow
through the atty and it's good to go. Very rare an old flavor will linger for more than a puff or two.
The disadvantage to taking it all out is....
The bridge, screen, and upper wick will allow an atty to hold a good 8 drops or so without flooding. That's pretty close to a real ciggy in terms of how long that load will last. Loosing the bridge and wick...means you have to drip more often and pay more attention to what you're doing when dripping.