What many folks have done is to attach some short pieces of square rod to the rail tops to lift their kettles up a 1/4" or more. Solves the problem with the right side design.
If the flat bottom pot diameter is large enough that it rests on all four square tubing segments, the design on the left side will only be modestly more effective than the one on the right, because even though there are four cut-outs between the bracket ends, the exhaust will still have to go down and under the square tubing to escape.
If you raised those four brackets so their tops are above the square tubing by as little as a 1/2" and made them strong enough to become the pot rests, that would provide a big improvement wrt "breathing", as the exhaust would then flow directly out and up.
But I think adding the square stock to the rail tops is easier and at least as effective if not more so...