Black Poly Plastic
My personal barrier of choice is black poly plastic.
It combines the most number benefits with the
least amount of drawbacks.
For one, the plastic comes a variety of size rolls,
but typically in 25 by 10 foot rolls. This allows
you to cover a lot of area with just one roll. The
fewer seams there are in your barrier, the less
likely weeds will find their way through the cracks.
Another thing to keep in mind is price. Plastic is
much cheaper than landscape barrier and gives
you the best bang for your buck in my opinion.
However, the downside to plastic is that it
doesn't drain as well as the fabric. The fact that
it "porous" like the fabric means that it doesn't
let as many weeds through, but it doesn't let
water through either. Thus, it is important that
when you put the plastic down you poke holes in
it to allow for drainage. I've found that a
pitchfork with thin prongs works well.