The biggest change is the move from an engine that was originally designed for transverse mounting to one that was always intended to be installed North-South.
When you look at the ancilary component design and intake the new engine provides a much better power unit package than the older roadster engine.
You'll have to give up some peak power for a little additional torque lower down. Ultimately, increased torque will make an average driver feel like the car is quicker.. so generally you probably won't notice any difference.
