Simultaneous attack and defence is something that sets Wing Chun apart from most other martial arts. Many styles talk about it but still do block and counter type movements. For many the pause between defence and attack (or lack thereof) is a measure of ability with transition between defence and attack becoming smoother and faster with experience and seniority eventually approximating simultaneous action in high level practitioners.
However within Wing Chun there are two ways to achieve this simultaneous attack and defence (if we ignore the third (and imho superior) option of using footwork and angles to perform the defence entirely negating the need for defence with the arms at all); 1) using two arms simultaneously e.g. tan da, pak da, wu da etc where one hand intercepts and "defends" (although normally also doing something to disrupt the opponent's posture, structure etc.) whilst the other strikes. 2) using the same arm to both intercept and attack e.g. intercepting with the punch, retaking the centre with a side palm, biu sao etc

There would appear to be a perception among some practitioners that method 2 i.e. intercepting and defending with the same hand is superior and demonstrates a higher level of skill. I wondered how the majority see this?
From a personal perspective I believe both have a place but use the single hand approach far more in emergencies and less as first choice due to the effect that the interception has of adding resistance to the strike thereby reducing its power, I would always rather hit with a free unobstructed hand than one that is slowed by friction through contact with an arm but its very much a personal view. What does everyone else think?