I don't know that there is a good answer to this question, other than trial and error in the type of diving you are doing. I certainly don't know the proprietary details of Pelagic's algorithms, but even if I did, it might not help to find an answer. Algorithms that might be in synch for a shallow recreational dive might diverge in a decompression or repetitive dive scenario. Or- much more likely- two computers might appear to be very different on shallow dives, as indicated by differing no stop times, but be quite close on deeper exposures.
How algorithms handle repetitive, multi-day, deeper than previous, deep stops, or if they are, like RGBM, oriented towards preventing bubble formation, all will create differing effects depending on the dive scenarios. There are too many variables to generalize- all I can say is that the root theory and calculations of all these algorithms are in the same arena- excepting that the Cobalt, if it goes deeper than 150', will use fully iterative RGBM, a much more computationally intensive bubble model. The Cobalt is generally middle of the road for overall conservatism. But differences between computers often seem greater than they really are, particularly on shallower dives.
Conservatism in dive computers is hard to nail down, but differences tend to seem more extreme in shallower, longer dives, because we treat deco/ no deco as a binary function when in reality is is a gradually increasing slope- very gradually increasing at shallow depths. So on shallower dives even a slight divergence in the algorithm conservatism can translate into many minutes more or less of no-deco time. The same computers might show much less difference- in minutes of no-deco time- at deeper depths. That probably accounts for some of the subjective differences in experience of how conservative a particular computer is.
Computers that show only a minute or two difference on a deep dive might diverge by many minutes on a shallow one. What you don't see is that one is "almost" in deco, and the other is "barely" in deco. They may not be, in mathematical terms, very far apart at all, but because they treat deco/ no-deco and a binary switch, one seems much more conservative. If it were displayed in analog terms, as say a % of risk, they might not seem very different.
A lot of divers see no-stop limits as falling off a cliff. But it's a lot more like hikers climbing a very gradually increasing slope, and deciding at what % grade to turn back. If one person decides to turn back at 30% and another at 32% grade, and they both head straight uphill, they will turn around at almost the same time. If they traverse the slope at a very shallow angle, the 30% hiker may turn around a long time before the 32% hiker. His turnaround point is no more conservative than it was going straight uphill, his risk no greater, but the difference in minutes between the two is greater because of the angle at which they approached the hill.
I realize this does not answer your question. But perhaps it can give you a little background with which to tweak the conservatism settings on the two computers, to bring the profiles into alignment for the type of diving you are doing.
Ron
