Mike,
The 48v mild hybrid can’t power the car alone, the petrol engine will be running all the time. The hybrid element is just a small boost to acceleration.
It is a good choice, you already know how good that engine is as you have it in your golf, the Leon has 20 more HP too.
Mild hybrid:
It’s a system that stores surplus energy in an extra battery and uses it to assist the engine during moderate acceleration. It’s a very simple system to produce, so it doesn’t bump up the price too much and only adds marginal weight gains, 6.8 kg in Suzuki’s case but the engine needs to run at all times and it doesn’t provide a significant power boost – in fact it is a very ‘mild’ hybrid system indeed.