I love how I keep hearing that the 2014 power units will produce as much power as todays engines, that is not accurate and doesn't compare like for like. Todays 'power units' produce around 750hp + 80hp (for 6.6 seconds) for a peak output of about 830hp. The 2014 units are reputed to have a total output of 750hp with 160hp coming from the ERS for 33 seconds. Considering that the average circuit lap times are about 1 minute 25 seconds, with full throttle applied about 65 to 70 percent of the time, average output will be way down.
Try thinking about more than "Ooh, shiny big numbers".
Let's say a current engine peaks at 750hp. What does this mean? Well, it could mean it has very little below or above this peak power producing rpm. So as impressive as the peak figure is, the engine will be woeful under acceleration, and woeful going past peak power in order to have the next gear ratio put it anywhere near the power band.
Let's say a turbo V6 has no better a peak figure. But the forced induction gives more power, compared to the current engine, both below and above the peak power rpm. This engine will accelerate better, and still hold on well enough after peak hp to allow the next gear up to engage within the usable power band.
If the engines are also more fuel efficient, the cars will have to carry less fuel weight, although as they're going to be Pirreli limited that's not likely to have as much impact on lap times.
To put the engine design differences another way - I can throw a hot camshaft in my everyday car and have as much power as the factory spec turbo version. Except the power will kick in for such a limited range that the car will be slower in the majority of situations, and most likely use much more fuel in the process.
And upon re-reading your post, I'm not sure how you're coming to the conclusion 750 + 80 for 6 seconds, is more on average than 750 + 160 for 33 seconds. Unless I'm mis-reading (only had the one glass so far tonight though).