I do not notice a flavor difference between my carboys (5 gal batch in 7 gallon carboys), my open fermenters, and closed keg fermenters (10-12 gal batch). I especially like the open fermenter for ease of clean up, don't have to use two separate carboys for the large batches, and especially like for those very active english yeasts that spill over the sides and into the bin I place them in (like top cropping). I do place a loose lid over the top to keep dust out.