I would get the KR because, it is limited production, fast and is The King of the Road. The car is powered by a 540 horsepower 5.4-liter (330 CID) supercharged V-8 variation with a Ford Racing Power Upgrade Pack. SVT and Shelby announced that 1,000 40th Anniversary Editions will be built for the U.S. in 2008, with another 571 units in 2009. This 1,571 production run matches that of the original 1968 GT500KR. In total, 1,746 units will be produced, with the extra 175 units going to other markets. It is a reintroduction to the KR that was released in 1968.
What makes it different from other Shelby's are, a carbon composite hood with scoops and hood pins, a lowered front air dam, and 14-inch Brembo brand front brakes with functional cooling ducts.
The suspension has been modified and tuned by Shelby Automobiles and Ford Racing including unique spring rates, dampers, stabilizer bars, and strut tower brace, all designed specifically for the KR.
It goes 0-60 mph in: 4.1s
And at a 1/4 mile: 11.92s @ 120 mph (11.58 @ 122 mph (196 km/h) on drag radials). The KR is the fastest out of all of them.
The Challenger I also like it is very retro looking yet, stands out from the crowd. All 2008 models were SRT8s and equipped with the 6.1 L Hemi and a 5-speed AutoStick automatic transmission, which outperforms the legendary 1970 Hemi Challenger. The entire 2008 run of 6,400 cars were pre-sold (many of which for above MSRP), and production commenced on May 8, 2008. You can get an '08 for about stock price now.
Don't waste your time on a Camaro, they aren't even out yet! I would also suggest looking at the Super Snake Mustang Shelby, those are NICE!