In all my experiences with tires, once I settled on 23mm on the rear, I never went to a narrower tire. 25mm for steeper tracks, but 23mm was my happy spot in the back. Better low speed handling, more predictable, and less skipping. Going from 19mm to 23mm is an 18% increase in width. Your contact patch not only widens, but also lengthens when you go to a wider tire given the same PSI. If you drop the PSI, you can maintain the same rolling resistance and increase this contact patch even more. You would have to fiddle with the pressure, but decreasing PSI 5-10% allows you to maintain the same rolling resistance (this is ball-park math). This slight drop in pressure can double your contact patch. The aero differences would most likely be immeasurable, but the traction you gain can certain be felt. This was always my opinion. The front wheel is more aero, so let its job be aero, and the back wheel is for laying down power.
Despite all that, 23mm just felt better and allowed me to ride at a lower speed, and that goes a long way in opening up your tactical toolbox for sprinting. For pursuit, you can try to go as minimal as possible without any detrimental effects. For a Kilo/500 I would want a bigger contact patch just for the start, and for Mass start racing, I would want that contact patch as well.
Just some info to chew on to help dial in your decision.