Which car is overall faster, a Porsche or Aston Martin

An Aston Martin Vanquish is faster than a Porsche Cayenne.

Almost anything (a Range Rover for example) is faster than a stock Aston Martin DB 5 according to the Top Gear power laps test.

WHAT MODELS THIS QUESTION CANNOT BE ANSWERED. BUT ALL IN ALL PORSCHES ARE FASTER.

Porsche, definitely. The Carrera GT is disgustingly fast. Porsche held the official lap record for the Nurburgring for a while, but things have changed. Aston is more of a Luxury brand.

Porsche 911 turbo is faster than a Aston Martin DB9. But the Aston looks better in my eyes.

lets compare their top cars, Aston Martin Vanquish S and a Carrera GT. The Carrera GT wins in both acceleration and top speed. 0-60 3.9sec and 330km/h top speed. Aston Martin has 0-60 in 4.8sec and top speed of 321km/h.

Porsche. There was a race between a Aston Martin V8 Vantage with 420HP and a Porsche 911 Carrera S with 380HP. The Porsche went around the track 7 seconds faster than the V8 Vantage. The Porsche is also have higher top speeds and are more aerodyanmic and lighter and better handling.
l provided a link to the race video.

Since no one is matching up any thing, why not compare the Vanquish to the Carerra GT..

duh!

these cars serve two completely different markets.

the Aston Martin in Brittain is supposed to be the quintessential Gentlmans luxury sports car..a Jaguar for the Royals as it were.

Even though Porsche is better in many performance categories, (not all) the Aston is an incredible spine tingling machine. Would l bash it into a curve the way l would a turbo GT...no, but I'd sure like to cruise the alps with a blonde.

The way to find the true speed of these cars is to look at a track test. There was one done by my favourite show, Top Gear:)
The end result is really interesting, and definitely solves your question. None the less, l wo not spoil it for you!
http://youtube.com/watch?v=XsrxdCb7eTk