It's "as good," but it doesn't have the same power. It's like a car-- sure, it'll cruise in low, smooth RPMs... but you have no pull to get out of sticky situation, or for any fun factor. It's got great mid-range, but no top end.
The 650 is much easier on the highway than any smaller cc bike. It's effortless on the motor and you've got plenty left. For what I bought the ER-6n for (commuting and touring), it's fantastic. Super comfortable, great fuel economy, plenty of power. It's just NOT a track/twisties bike. The suspension is too... "budget." Again, great for long highway trips and around-town commuting, but not for aggressive or spirited riding.