I have an Edgi 6.01mm barrel and it's very nice. With a CA G36 hop up unit, Systema bucking, stock nub, Edgi 6.01m barrel, Guarder SP110, (and other upgrades) and G&G .25s, I can engage a target smaller than a torso sized target fairly well from 170 feet. From 150 feet, 6 inch wide trees don't stand a chance.
From what I've been reading lately, once the tolerances of barrels get to a certain point, it doesn't matter anymore because bbs will never meet those tolerances of the barrels. So basically, any top barrel brand will perform roughly (I mean a lot of bbs have like +/-0.1mm, while a good tightbores have like +/-0.0015mm. I don't think that will matter considering how much the bbs vary. lol Bore size doesn't matter, the quality of the crown, hop up cut, inner smoothness, and roundness matter the most.
Go for a barrel with a larger bore. (6.03mm would be my choice) The tighter the bore, the more is will "react" to imperfections/deviations with bbs. Namloot and Golgo 13 have found TM barrels to perform the best. Namloot claims that his Prometheus/Madbull tightbores give no boost in accuracy over his TM barrels, only fps. I wouldn't be surprised.
The "tighter the bore the more accurate seems to be a myth" and I haven't found anything that proves such a thing.
Long story short, Madbull would probably be fine. (I've heard good and bad things about Systema) Prometheus would probably only be worth it if you don't have a very stable outer barrel or something because it would resist bending more. (like a barrel extension)
Just so you know, Madbull barrels have actually been found to have a 6.01mm ID, instead of the advertised 6.03mm. (according to the German dude who did all those barrel tests with that snazzy machine lol)
Hope this helps and sorry if this is a bit late.