Had to sit down and read the original post twice, but here is what I came up with. I am a pilot and have no aerodynamic training beyond what is required for an ATPL, so I might not be using the correct terminology.
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Wing loading and G loading are not the same thing. If both planes fly at the same speed and bank angle (and experience the same G loading as a result of this bank angle), they will have exactly the same radius of turn.
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I'd say that when comparing two airframes of similar weight but one with twice the wing loading (ie half the wing area), the aircraft with the higher wing loading is most probably designed to fly significantly faster. Therefore, with both at their design speed at any given bank angle and hence G loading, the faster aircraft will have a greater radius of turn. If both do fly at their design speeds, they could well fly at a similar angle of attack and there is no reason why the faster aircraft would 'run out of spare angel of attack' sooner than the other.
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Now, if both of them do fly at the same speed (the design speed for the slower aircraft), the aircraft with the higher wing loading will be flying closer to its stalling angle of attack, to compensate for the loss of speed.
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If in this situation they both fly a turn at a given bank angle the radius is still the same. However, the faster aircraft will be the first to reach a bank angle (and associated G loading and angle of attack) that will make the wing stall.
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So, at slow speeds the aircraft with the lower wing loading could out-turn the one with the higher wing loading. But only because the aircraft with the higher wing loading is flying at a speed it is not designed for (ie too slow) and would be the first to stall.
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Hope this make sense and that I haven't upset too many of the pros on here by using the incorrect terminology.
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