Rand's point is that for attacks on foes of the attackers caliber a 50OB swing is a big deal and he's right. That was exactly my point. If a 50 point swing doesn't impact your characters ability to land a good blow then it's unlikely you're fighting an equal foe in the first place (not a good baseline to try and balance from).
Now, yes, at VERY high levels that gets more tricky, but how high are we talking and how high of level do you think the average RM user goes? From my experience around here people typically don't even see 10th level. I think I've known one or two people to comment that they've gotten into the 20's even.
Yes, I agree that few games get past level 10. By that point, I would say that semis and casters are starting to surpass NSUs in RM2, though the gap is not huge at that level either way you judge it.
In RMU, I think the level at which semis and casters start to surpass NSU's is lower, due to all the things that enhance casting in RMU. However, even by level 10, NSUs do now (in RMU) have the advantage of the quick attack I outlined above. A level 10 Fighter can be expected to have an OB in the vicinity of 150 (100 rank bonus in a professional skill; +30 for stats; +15 or 20 for Item). That means his choice is between a single +150 attack or two +100 attacks.
+100 attacks still have a very high chance of success, especially if you get two of them. These attacks are especially useful against casters who might cast things like Bladeturn I since that blocks only one attack. Some casters might cast Bladeturn II, to block II, but that's a level 11 spell, and of course we haven't even talked about the Fighter using multiattack here (which is the real key to boosting high level arms users). One or more of those attacks is very likely to get through.
You're right about comparing apples to apples, but remember that the core comparison here is between casters and NSUs. I don't think there are too many casters whose defenses could handle multiple +100 attacks per round. Casters tend to have lower defenses, which is why I brought up the point that even with a -50 penalty, an NSU has a good chance of injuring a caster.
In any case, the central point I am making is that NSUs in RMU have an additional tool that they did not (AFAIK) have in previous editions: the ability to make two quick melee attacks per round without having to develop any special skill for it. In some cases, this will mean NSUs being able to kill literally twice the number of opponents per round they would have in RM2. This I think gives a significant boost to NSUs.