I have both the 20L and 30L and absolutely love them. They are seriously heavy duty plastic with two big handles on the side which makes carrying them easy and safe. The large screw on top makes cleaning them really easy, as you can get your hand in there to scrub if needed. I really like the giant 3-piece airlock, too. Less need for a blowoff tube, though I still use one on really big beers. They only drawback I have experienced is that the plastic is not clear, so you can't see into them as well as a plastic carboy. You can see the level of the liquid, though. For me, that's a minor issue compared to all the positives. I'd go with the 30L if you mostly do 5-6 gallon batches.