I'm afraid I don't understand the question. The quantum yield is a molecular parameter and is not determined by the measurement technique. In principle both techniques should give you the same value. If you are consistently measuring a higher value with one technique over the other, then there's something that's introducing a systematic error into the measurement.
Most people (>99%, probably) determine QY relative to a standard because this method doesn't require specialized equipment. It is also an easy measurement in practice. Unfortunately many people don't do it very well because there are a lot of places to introduce significant error - starting with the choice of reference standard. If you have the right equipment (and knowledge) to measure QY directly, with an integrating sphere or some other method, then that'd be the preferable way to do it. The relative technique is a well-accepted alternative, though, provided you do it carefully.