I have read that recently last year that Red Bull racing cars have the best chassis. How do we analyse the chassis of an F1 Car? what is the science behind the best chassis and the worst?
There are various aspects to what makes a good chassis.
The ideal chassis gives lots of downforce to be fast through corners, but has little drag in order to be fast in a straight line. Unfortunately adding downforce tends to add drag, so it's a trade-off.
A good chassis also gives consistent downforce: it's no good if it only provides downforce when travelling straight, and not when turning through a corner. It should also provide balance - i.e. similar amounts of downforce on the front and rear wheels; if there isn't enough downforce on the front wheels the car will understeer; if there isn't enough on the rear wheels it will oversteer.
Generally when F1 commentators and fans talk about "the best chassis" they're talking about the one that produces the most downforce, i.e. is fastest through the corners. Telemetry from F1 (not always publically available as far as I know) can show the minimum speed a car has used when going through a corner, the higher the minimum speed the better the chassis. Articles such as this German GP one from formula1.com compare relative gaps in seconds between the different teams in slow, medium and fast corners, as well as on the straights. (As speed is distance/time, then comparing time through a corner is effectively the same as comparing who carried the most speed through the corner.)