HPS lights are more efficient than flouros. In other words, they put out more light per watt of power usage. More light = more bud.
Also, on the heat issue, you have been misinformed. Whilst flouros are cooler to the touch, they actually put out more heat into the growroom than the equivalent wattage of HPS. The difference is that flouros put out mainly convected heat, whilst HPS put out radiated heat. This means that there is a hot "bubble" around the HPS, which means that you can't put the plants too close, but they more than make up for this in light intensity, which in return makes bigger buds.
Flouros are only a better choice if you have limited headroom, and can't raise your lighting enough to account for the bubble of heat around the HPS.