Originally Posted by Iride01

If it were the same exact material, then maybe you are correct. But newer versions of carbon fiber cloth and resin, as well as better design internally for the lay up can result in a stiffer and lighter frame.

I don't know if that is the case with a 2013 R3 vs a 2013R4. But I hardly think it important to argue whether it is or isn't.

We both probably will agree the OP just needs to ride them both. Assess the condition of each. And pick the one that is favored. Neither will be a bad decision if the bikes are in good condition and everything works.

Here is a article on 2013 Cervelo R3 and R5's. I tend to like BikeRadar's reviews. The OP might find it useful or not. It doesn't really get into riding qualities. https://www.bikeradar.com/news/cerve...kes-first-look

But perhaps with some searching the OP can come up with some road test reviews for the individual models on BikeRadar or another online bike magazine.