I personally prefer having them all converge at one distance, particularly on the .50 equipped aircraft. The 'scissoring' or 'harmonized' or what have you, I do not like as well. Your fire is more dispersed, and you have no spot where it's really good, it's just this broad spread of weaker fire.
I realize it sounds simplistic, but your convergence should be set to where you do most of your shooting. I do a lot of BnZ, my convergence on all the .50 equipped planes is 450. This gives me a good 'zone' between 400 and 500 where my fire is quite concentrated, and allows me to put a lot of rounds on them, at those ranges because when I'm BnZing that's generally where I'm firing for effect. At closer range, my bullets go into two groups that I can generally put onto the enemy's wing relatively easily.
The other reason I like the slightly longer convergence is because it allows me to reach further to get a guy to wiggle if he's running away at 600 yards or so but not maneuvering. You can quite often get them to break if you hit them out that far, and a close convergence is much harder to aim out that far.
In a plane I tend to turnfight in a lot like a Spit 9 or something, I bring my convergence in around 250 or so because that's where I'm doing most of my shooting.
The main thing I find is, pick a convergence and stick with it for a while (a couple weeks anyway IMO) to see how it works for you. If you're constantly changing it, you're not giving your brain a chance to adjust to your bullet trajectory and have it become second nature.
Wiley.