In shooting RAW photos, which SD Card is faster?

I would just like to know, in the photography world, SD Cards have different "CLASSES" right? 2, 4, 6, 10.

Now, if i shoot RAW on my Nikon D80, and do it burst (let's say i'm doing sports) Does it make a difference in terms of WRITE SPEED Between a Class 4 SD Card and a Class 10 SD Card?

In which is it a fact that if i use a class 10, it will write faster, thus not lagging in bursting.

It could be that your older D80 can't utilize the higher write speeds found on Class 6 or Class 10 SD/SDHC memory cards. That fact and the size of the D80's buffer is much smaller then current Nikon dSLR cameras.

The D80 has a maximum burst speed of 3 fps, up to 23 JPEG, 6 NEF images. That means that really no matter what SD Class card you buy, the maximum burst time would be two seconds before you would have to wait for the images to write to the card in any case.

What is the purpose of shooting bursts of images? If you really, really need to shoot long sequences of back to back images, you will have to upgrade your camera, NOT buy a faster memory card.

Frankly seasoned sports photographers shoot at the peak of action and rarely use the burst mode on their camera

Looking at http://www.robgalbraith.com/bins/multi_page.asp?cid=6007-8531 I get the impression that a class 10 card may be overkill. An extreme 3 should be able to do significantly more than the not quite 10mb in that test.

Also, even if you get really quick cards lack of proper care will quickly kill any speed advantage so try to get in the habit of starting out a shoot with a card that's freshly formatted in camera.

The Class of SD cards is supposed to indicate their sustained memory throughput up to 10MB/s, so the higher the class the better (to a point).So class 2 is 2MB/s sustained, class 4 is 4MB/s sustained and so on.

As a rule of thumb, if you can go one class higher than that recommended by your camera supplier then you should be okay. By going one class higher it just gives your camera a bit more headroom to cope with very minor timing issues.

So a D80; well it's a bit of a dinosaur, I'd guess it's spec is for a class 2, maybe a class 4 card, so to be sure you'd only have to go for a class 6.

There's not much point in going any higher than a class or two above spec, as in most cases it's going to be the image processor (can't remember if the Exspeed in your camera is Fujitsu or Sony based) and any buffer memory that limits the throughput when burst shooting, so just going higher and higher offers no benefit.

My EOS450D can buffer 4 shots in raw +jpg mode - around 16Mb per shot. The card makes a HUGE difference in burst mode.
With a Sandisk Ultra card (not sure what class) I get 4 shots then a LOng wait while the card catches up
With a Sandisk Ultra II (class 4) I get 4 shots and then a short wait while the card catches up
With a Sandisk Extreme (class 10) I get the 4 shots and the card is far enough ahead to give me number 5 with a barely noticeable delay. Numbers 6 to 9 (never taken more) follow on a little more slowly but better than 1 shot per second.

The other advantage of the faster card is that it takes less time to download to the PC.

Data travels from camera's processor to buffer and then to the memory card. One of these is the bottleneck, usually memory card.