Through personal experience, I have found that the higher cadence method will always get me ahead of the group of commuters at the lights. I sometimes see the standing grinders but by the first downstroke of their crank arm, I am already gaining much more acceleration. The grinders are also wobbling all over the place because their centre of mass is much higher and the bike is harder to keep in a straight line.
I think you will need to experiment with which gear you start in while accelerating in the saddle.
I commute on a Trek FX 7.2 and have found my most effective starting gear is using the middle front chain ring (the 38 of 48/38/28) and the largest rear sprocket (the 32 of 11-32, 8 speed).
Once I am spinning at a cadence which is around 80% of my physical limit, I then momentarily relieve the tension in the chain and change one gear (change up rear sprocket). It takes a bit of practise to get this right but it avoids the gears clunking while you shift.
Another benefit of starting in the 38 front chain ring is that I can accelerate to beyond my cruising speed in this chain ring. If I were to start in the 28 chain ring, then I would need to lose some acceleration while making the shift to the 38. A shift between front chain rings is much more time-consuming between a shift between rear sprockets.
I also make sure that my saddle height is correct and on the limit of being too high. With a lower saddle, it will be near impossible for your legs to transfer power with a high cadence. When I am at the lights, I need to fully extent my leg for my toes to reach the road. While I do this, I keep my other foot on the pedal in the ready-position. As soon as the lights change, I apply power and my extended leg has to 'catch' the spinning crank arm.