I doubt anyone could feel less than a 10hp difference, reliably. 2hp, definitely not. If the torque curve is similar, the engines will feel the same.
Sadly, everyone looks at a few numbers (hp, torque, 0-60) and uses those to decide which engine is better or worse. The reality is that most drivers would prefer driving a lower-powered engine that had more torque lower down the rev range, as they would think it was "more powerful".
BIKE magazine even conducted a serious test of this many years ago, getting less extreme camshafts cut for a bike engine and fitting it with smaller carburettors. Everyone, except actual racers, thought that the detuned engine had more power and was nicer to ride - because it did have more power, at the revs street riders used every day.
A US study showed that majority of drivers never (repeat never) use more than half the rev range or more than half the throttle travel - which shows exactly why some drivers think the Mini's Sport button is good, because it increases the perceived power. Chrysler even went so far in the US as to recalibrate their throttle linkages to give the same effect all the time.
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