Scandisk Extreme III Vs. Lexar Pro's

Just wondering if anyone can tell me if there is honestly that much difference in the speed and quality of these 2 memory cards that justifies the price difference?

Many will argue this point. Unless you max out your buffer you will not see any difference. For example I do a lot of product photography. To save money I buy the cheep house brands. They are like 88X or 100X. But I can get a 4 gig for $25. When doing products I never shoot more then 1 shot at a time. So if it takes 5 seconds to write to the card, I dont care. Im not ready to shoot the next frame that fast anyway. Now if you are doing something with action, and constantly fill your buffer with continuous shooting, you will want the fastest card you can afford. It will make a difference at that end. It may clear the entire buffer in that same 5 seconds.

It really comes down to how you are going to use it, to whether it is worth the money for you. You will most commonly feel the difference when you unload through the card reader. They unload at max speed. But if you have stuff to do while it unloads, again, it does not really matter. With my slow cards I throw them in the computer as I clean up the set. I never "wait" in it. However slow it is, its done by the time I get back to the computer.