Princess, the 23's do have slightly less rolling resistence then the 25 and they weigh less. But the advantage to the 25 is on the road where ruts, grooves, pavement edges etc can make a 23 follow those things which could cause some interesting handling situations, whereas the 25 would mostly just roll over that stuff.
If the ride is too harsh for you, you may want to try dropping the air pressure a tad. I weigh 163 and I only put 95 in the rear and 85 on the front (these are 25's, when I ran 23's I ran 10psi more); and been doing this with Armadillos for 3 years with no probs. If you weigh less then I then you could even go less; but experiment to find the perfect pressure for you. If you put max pressure in your tires and don't weigh a lot you could also find the tires skipping over rough services.
Keep in mind these tires are not racing tires, they are a superb commuting/training tire if flats are an issue. One thing you can do to keep the overall weight down as much as possible is to use ultralight 65 to 70grm tubes. But if you decide to race your going to want to use lighter tires for the race.