The purpose of installing headers is to isolate the exhaust pulses fom each other, aiding the sound wave in both intake "filling" and scavenging of exhaust gasses. A "3-tube" header cannot achieve isolation, as two exhaust ports are "talking to each other" on each side. If the heat crossover is not blocked or "filled", you then have FOUR cylinders "cross-talking".
Again, headers should NOT be bought based on "ease of installation". Easy ones are seldom good ones...