Renault's 2011 car has impressed leading designer Adrian Newey more than the latest single seater produced by Ferrari.
"The Renault has impressed me the most," Red Bull technical chief Newey said in an interview with Spain's El Pais newspaper.
"It's exhaust system is completely different to the others. I haven't analysed it deeply but the path they have taken is completely unique and very brave, and that's always good," he added.
As for Ferrari's 150 Italia, Newey said it is "a conventional car".
And McLaren "have worked hard on the sidepods, which are different, but I think the change is more visual than anything else.
"I think the vast majority of teams chose to evolve their previous cars," said the Briton.
For that reason, Newey said rival teams subsequently copying the dominant RB7's exhaust layout is simultaneously "flattering" but also "irritating".