I will try to make my point of view about the exhaust systems of Ferrari, McLaren, Sauber and RBR as clear as possible:
1) All of them try to "seal" the diffusor with the hot exhaust gasses to increase the downforce. It allows to run a relative high rake. The theory was already discussed here and in other places.
2) The RB7 pioneered the most effective way [and most copied] by ducting the hot gas as close possible to the key areas right between the diffusor and the tyres. This way a very high percentage of the exhaust energy could used for the intended purpose (1). This in turn made off-throttle blowing even more attractive, complicated engine mapping a must and mandated a bigger fuel tank for it's heavy use during the races.
3) So how they want to achieve that?
a) McLaren and Ferrari try to blow it into that area over the strong airstream flowing around the low part of the sidepods. Thus the Ferrari elongated sidepods and the McLaren bulge.
b) Sauber and Red Bull try to blow it into that area along/aside by attaching the exhaust gas on a surface. Thus Sauber and RBR have that sidepods ending into a ramp. This creates problems with the strong airstream flowing around the low parts of the sidepods which were formerly 'solved ' by adopting a smooth coke bottle rear.
4) So why the so much fuss about the RBR and not the Sauber?
The RB8 has undercut sidepods, a considerable tunnel ducting a good deal of airstream coming around the sidepods which should considerably lessen their negative impact on the 'ramp' solution. The exhaust ducts are also bend outwards so that the plume attaches mostly on the outside of the ramp, right behind the entrance of the sidepod tunnels. There are also long small vanes in front of tyres to fence the hot plume in and to direct it into the sides of the diffusor. (The design of the starter hole and it's blowing by the interior channels of the tunnel is also very interesting but not as central to the topic).
5) What is best?
Impossible to say. Ferrari and McLaren have a clean lower cokebottle but have elongated and bulging upper sidepods ends and lack a physical surface to attached the exhaust flow which might reduce the amount of it reaching the intended areas. Sauber has said surface with the ramp but has to give up the lower cokebottle shape. RBR might have by the looks the best of both worlds but the whole package looks very complex and challenging.
6) Is it easy to copy?
It depends a great deal on the internal layout and packaging of the car and the complexity of the various solution. To make an example the DD was much easier to copy for some teams then it was for RBR has the whole rear was packaged in different way. My personal guess is that the RB8 system is due to it's level of complexity and deep integration into the whole car design the most difficult to copy, but also the other will take very considerable effort especially due to the lack of testing and as great deal of the sidepod design has to be completly changed. As I said before the amount of effort will vary from car to car depending on the specs of the 'copee' car and the 'copycator' car.
Of course this is all just my personal opinion, based on a decent study of all available material.
Edited by H2H, 04 March 2012 - 10:48.