M5 Expert (>4000)
Join Date: May 2009
Location: Phoenix AZ
Thanked 656 Times in 525 Posts
With a supercharger you may not notice any perceptible lag, but you will not be able to achieve the power you want as easily. Superchargers sap power from the engine unlike turbos that use "free" power from the exhaust to feed the engine.
Especially with the reverse-flow architecture of BMW's turbo V engines, turbo lag is essentially something of the past. You feel the throttle response as fast as you would with an N/A and the engine will start making power almost immediately after. This isnt like old times where turbo lag was a fact of life - you would floor it, have a coffee, wait for your turbo to spool, watch a movie, then your turbo is spooled and you are off. With modern technology we have created turbos and engine designs that give you no perceptible turbo lag or throttle delay.
So essentially it comes down to using a S/C which saps power from the engine or a turbo which gets more power and isnt extra load on the engine.