In a house with young children who are smart enough and/or tall enough to
reach the sink (or toss something in while you are working there) a batch-
feed disposal is best. The disposal will not run unless the lid is locked
into place. That means no one can stick a hand (or a small foot) into it and
be injured. It also means nothing can accidentally fall in while it is
running.
Batch-feed disposals match their names. You put a batch of garbage into them
for grinding, then you lock the lid in place and, with the water running,
turn it on and the work is done. You then open it, add the next batch and so
on.
A continuous feed disposal can run continuously as you feed more garbage
into it. It is faster to run but you do have a risk that someone could
accidentally turn it on while someone's hand is in it or that a toy or piece
of cutlery can slide into it as it runs.
Wall versus air versus cover control refers to how it turns on, with a wall
switch, with a button that turns on a hidden, interior switch with a blast
of air, or turns on only when the cover is in place.
Pros and cons:
Batch-feed - no risk of sticking a body part or foreign object into it while
it is running; takes longer to grind the same amount of garbage because of
stopping and starting and lockingg/unlocking the lid (and if you lose the
lid it won't run).
Continuous-feed - very quick and easy to use but you run the risk of it
turning on when you have a hand down in it.
Wall switch - standard installation, easy to set up and fix but you run a
slight risk of electric shock if your hands are wet when you turn it on and
off.
Air switch - no risk of electric shock but less common and harder to repair.
Cover control - no risk of ther machine running with something in it that
shouldn't be, but if the cover disappears it doesn't run.