I believe AeroGrow started the business with the 7-pod Classic Aero Garden
and still sells it. It has the ducted grow-surface with water pump that
requires an electrical connection. The seed pods are short because they are
bathed in nutrient-rich water pumped to them by the pump underneath the
grow-panel, so they don't have to be in contact with the water. It also has
two compact fluorescent grow lights, each with 6 bars clustered in a circle.
The electronics that controls the timing of the lamp and water pump is in
the base with programming allowing you to select the lamp timing to match
the needs of the plants.

Then they came out with the 6-pod - - probably they changed the pod number
as a way to tell them apart just by looking. But the 6-pod is quite a bit
different. The grow panel is now just a plate with holes in it - - no pump
and no ducts - - very simple and easy to make - - should be cheaper - -
yeah, right. The seed pods are longer so they can dip into the nutrient-rich
water, and there's an air bubbler in the center that produces some agitation
of the solution in addition to assuring 100% humidity in the air under the
grow surface. But the two grow lights are different and probably are more
efficient at providing light because all 6 tubes of each are flattened out
into a plane array instead of clustered together. The electronics appears to
only control the light, allowing the air pump in the base to run
continuously as long as the unit is plugged in.

So what does all this mean? The older 7-pod design has a few problems with
the pumping of the water to each seed pod. When the seed pods are started,
before any roots reach down to the water, they produce the sound of dripping
water. It can be minimized by keeping the water at the top level, which is
easy when the plants are just starting, but the sound of dripping water
doesn't go away until the roots reach the water - - in a couple weeks or
more. The pump eventually has to contend with root debris in the water, so
there's a filter in front of the water inlet to the pump. As long as the
filter is in place and not clogged, it should be fine. But over the growing
cycle the pump has a lot of work to do, so it can be a weak element in the
design. In addition, the ducts in the grow-panel are almost impossible to
clean, and so might clog or transfer plant problems if water pumped into
them isn't debris free - - a risk if the unit is bought used. Sanitization
with bleach should help with plant disease, but not clogging.

AeroGrow then came out with different products that they felt they could
sell for more money. They were all in the 7-pod family. Some had separate
programming of light and nutrient pumping that was supposed to be optimized
for the various plant families. They improved the light hood with three
plane-array lamps f or greater light output, and offered a longer support
post for growing taller plants. Unfortunately, the 6-pod design did not
support the improvements and so became a dead end so to speak.

For trouble free operation, I tend to prefer the 6-pod - - it is simple and
straightforward. If feel you might later want a fancier and taller plant
growing experience, the 7-pod allows improvements.

Oh yes, there is a 6-pod unit that has the simple grow panel and also the
three plane-array lamps and tall support, called the "Aero Garden Elite 6+",
but the "Deluxe Upgrade" that equips the 7-pod with brighter lamps and
taller support will not fit on an "Elite 6" base. The "Elite 6 plus" is a
totally separate and unique product with no upgrade path from an "Elite6".