Revs/volt unloaded is like saying a Honda S2000 sportscar engine will do 9,500 rpm on so much fuel, and a Bugatti Veyron will only do 9000 rpm on the same amount of fuel - when both are standing still! Both those statements are true, but have no bearing on the performance of the vehicles they are in!
Forget the revs/volt (and come to the battery C rating and servo speeds!) and look at the performance you want in the car. Go with the recommendations of others, or experiment for yourself. Relying on the numbers on a box or label is unreliable unless you can get all the data behind the results being published. HTH
You would have to undergear by a large amount before doing significant damage to a motor. The situation is worst when you undergear a lot and use a lot of timing advance. If you want to soften motors up a bit, go for reducing the timing first, and then the ratio. HTH