B,
Talk about asking the right question!
Last week I sold my Mavic Aksium race wheels and put on a pair of Kinlin 279 (23mm wide, 28mm deep) 24/28, radial/2X, x-ray spokes, Novatec hubs... and it's like night and day. Being a bigger guy, I felt like a gorilla on a tricycle on the Aksiums. Wheels rubbed pad to pad on standing climbs, they were noodly, soft, and I was being robbed of power. I could feel it. Out of saddle sprinting was out of the question, and the bike cornered like unpredictable crap.
The new wheels transformed my bike for sure, and it's clearly perceptible. The bike is more rigid, all my energy gets put down onto the pavement. From clip in and push off and that first press on the crank, everything is more solid. I can now get out of the saddle and sprint - f** yeah! - and I no longer feel like I'm climbing hills of jello.
Maybe the Mavic's werent tensioned properly, who knows, not looking back. I sold my year old Aksium set on ebay for $150 and it got snapped up quick.
There's a switchback here which descends from a cliff here, before I would have to bleed off a lot of sped and precariously wrestle with the bike on the hairpin. I can now do this faster...and most telling of all, I can start on the outside of the curve and keep driving the bike to the inside line coming out on the inner curb... before things were all over the place.
I'm 200+, so maybe this is what cause the Mavic's to show their bad traits but the difference is perceptible and it is the best $350 (500-150) I have spent on my setup. When I think back I can't believe how much those wheels flexed, pinged and labored under me. Any chance your Aksiums make pinging noises (spokes) when you're climbing out of the saddle?
It's interesting that the one trait of 23's - improved ride quality - I have not been able to pick up on. Maybe I need to play with tire pressures but these aren't plush by any means. Just stiff, fast and predictable. I have 25mm Gatorskins and on the 23mm rims they are f-l-u-s-h with the rim... very nice.
In summary, and to a certain extent depending on your weight, IMO you will see a noticeable difference in power transfer and handling.