the two cars!
Well, the R8 has more power, but its sweet spot in the power band is in the higher revs, and it's a good 400+ pounds heavier. But 525 normally aspirated ponies is still a fair bit of power. And quattro puts that power to work, though there is a slight perception of lag before all four tires grab and go. So, off the straight line the R8 is faster, though these days, it's not easy around here to find a safe place to really test it. The Jag has better, nimbler steering, especially in tight corners, though you do feel like you're moving a lot of mass around up front. The different engine layouts, and the significantly different visual cues out the windshield, produce very different driving experiences for two cars that are almost identical in length and width. Both are an absolute blast to drive.
2014 R8 V10 S Tronic Spyder Daytona Gray/Black Optic/Euro Tail Light/HRE P101 | 2013 A7 Prestige Quartz/Light Gray/Innovation/20" Sport