Where the Ferrari F1-75 and the Mercedes W13 were already vastly different beast when it came to sidepod design, their 2023 contenders are even more contrasting.
Taking a quick look at the way they have approached the airbox and engine cover design it is clear that Ferrari's SF-23 has a very slim, triangular airbox that rapidly converges in the flat, black vertical panel required to meet the minimum surface regulations. The bodywork at the back is so closely packaged that you can virtually follow the exhaust lines.
Mercedes on the other hand have retained a fairly large air inlet above the drivers head, meaning both teams continue on their own development paths. It's also clear that the car's "shoulders", the bulges that extend from the halo pylons towards the back are very elaborate and uniquely feature a wedge to guide airflow towards the back of the car.
The big difference for the sidepods here is that on the Mercedes there is a huge gap that allows airflow to pass around the sidepods and through the rear suspension elements onto the top of the diffuser. The Ferrari on the other hand likely has more components positioned lower down to the ground for a lower centre of gravity while aerodynamically relying more on flow over the sidepods. And what to think about the rear wing efficiency that is likely negatively on the Mercedes...
Time will tell which one is better. One could argue though that Ferrari's approach - a continuation of their 2022 concept - already proved its worth.
Also note in the picture the difference between the single pylon rear wing support and the double pylons and Ferrari's series of winglets around the airbox.