BMW M3 vs BMW Alpina D3 (Diesel). Would you save a little and go for the diesel?

Steve Sutcliffe has the keys to two very fast versions of the BMW 3-series: the 435bhp petrol BMW M3 and the 345bhp diesel Alpina D3. Should you satisfy your high-performance saloon cravings with a petrol or a diesel engine? Let’s find out.