If we assume consistency as stated, then surely the size they put on is totally irrelevant? Trader A harvests double the number of points per day per contract as Trader B so (s)he is clearly the superior trader.
But perhaps you are implying that whereas Trader B has a lot of confidence in their method, Trader A lacks it and the disparity is reflected in the size they put on. If this is the case then there might be some reason for choosing B.