Tyre Width: Aero vs CRR

One for the CRR geeks! Looking to dabble in TTs this season with my road bike, and I have two wheelsets available, one 19mm ID and 26.5mm external, the other 21 ID and 32 external. The roads are in Oxfordshire, generally poor quality with lots of road buzz and the occasional breaking up of tarmac.

Am I better off using the wider wheels with 25c tyres, or the narrower wheels with 23c? I’ve seen studies both around the aero benefits of a narrower tyre/rim combo with less frontal area, and also the benefits of CRR with a wider tyre. How can I tell which way to go? Does poor tarmac quality push me towards the wider option? Is the difference so small as to be negligible?

I’m making the assumption that the tyre/rim interface will be equally good between both sets, and running equivalent pressures (higher on the 23s), but feel free to school me there too :slightly_smiling_face: