In the absence of "hard" data, Id say this is a case of six of one, half a dozen of the other.
However, the main attraction I see in the 3 left, 1 right, 1 guard is that the 4 attackers spend all their time attacking. They never stop. This means they get full use of their buffs (alphas, betas, sensor scans, whatever) and better rotation of those abilities. As opposed to two people being forced to switch off every 15 seconds or so to kill probes, then come back.
Plus, the person detailed to kill probes in each of your sub groups is either going to have to evasive out wide or spend a fair amount of time in range of and taking fire from the gate, which can one shot people or similarly ruin their day.
As far as efficiency goes, 1 person detailed moving back and forth and spending the majority of their time attacking (done correctly you will spend about 6 seconds traveling out of every 22, the rest of the time spent dps'ing [I can average 4k dps just doing probes over the course of a KASE, and this does not include the Donatra fight]) sounds far more efficient than two people having to break off periodically, avoid the gate, avoid getting snared by tractor beams, have the appropriate skills off CD to take down the probes in a timely fashion, etc etc etc.
It might be worthwhile to try and test each way, same people running both multiple times each. But personally, Im going to bet on the method that keeps as more people on target, longer.
You make a good case, mayhaps I had indeed overestimated the travel time between left and right probes.
The Gate is no big issue so long as you don't fire on it, its fire will be spread out and easily handled (sometimes, it doesn't even fire at all).
Never been oneshotted by a Gate, they hit hard but don't oneshot.
Evasive is there to be used and all builds should have means to handle Tractor Beams, should they not?
In any way, I'll recall my words until further testing. I think we'd need to demonstrate the respective methods to each other, tbh.