If you go with a vented gas log install you will certainly have to
commit yourself to having the chimney damper removed or clipped or
disabled in the open position according to current code for vented
fireplace install. This means you will have a gaping hole to the
outside all the time. You can use a chimney balloon to act as a damper
if you are commited to a vented gas log, or if you already have one
installed. Many gas log owners are surprised to find that their
fireplace flue damper has already been disabled when their original
gas log was installed. The code to disable the damper alone, is often
an adequate reason for a homewowner not to go with any vented variety
gas log.

In the ventless model you do get the benefit of retaining all of the
heat if you keep the damper closed, but any of the CO, CO2, Nitrogen
or moisture that it puts out will enter your living area as well. In
the winter when your home is closed up you really want to minimize the
extra polutants you introduce to your already recycled inside air.
This is not just wiith the fireplace, this goes for candles, sprays,
paints and other pollutants. You obviously cant avoid these items all-
together, but do you want to introduce new contributors like a vent-
free fireplace?

From you original question I am sure you have your heart set on a
vented gas log, and you were just looking for brand name references.
But please take into account other options like electric fireplace
inserts if you are looking for firepalce ambiance, or maybe even a
candelabra with candles burned with the damper open as other suitable
ambiance option that wont cost you in heat loss.