My personal opinion is that once you no longer need a vacuum supply line to vacuum operated petcocks (to hold the fuel flow valve open). There is nothing but disadvantage left in continuing to have barbed carb holder boots. (If you're using OEM carbs) The carbs themselves have ports in which to mount a spigot for a vacuum synchronizing line.
The barb itself can come loose, leak and/or the cap fails,falls or gets blown off with a backfire and just plain adds to the air leak possibilities without justification of need. A "simpla-fi" as far as I'm concerned.
However, the biggest problem with barbs is this....they are usually implanted into the already molded rubber part and this always weakens the integrity of a molded part.
Almost all molded rubber and plastic polymer parts are like molded chains. In fact, they are just that, cross-linked (vulcanized, thermoset or crstallized) polymeric chains and are therefore, no stronger than their weakest link. They are protected by molded in skin or surface integrity effects. They are weakest at molded in knit lines and usually very much weakened by notch sensitivity by being cut, drilled, tapped or ground. They not usually well repaired to as molded property profiles. Sharp edges are to be avoided as they will almost always fail at points of stress point concentration sensitivity as well.
Pure and simple....once most rubber and plastic parts are notched, cut or abraided those cuts propogate very readily and that propogation is enhanced by a wide variety of chemicals, solvents and heat and pressure. Implanted barbs can do nothing but damage a molded rubber part.
A carb holder boot without cuts, notches, drill holes or points of high stress concentration is a far better more chemical resistant one than the opposite. No adamant need... no barb! Blue
