Extreme III vs Extreme IV - CANON 5DMKII

Please help

I'm trying to find any info on the web that can help me on the differences betwen Extreme III and Extreme IV SanDisk Cards to make the better choice to use with 5DMKII.

Any experinces with 5DMKII users or articles on the web will be much apreciated!
Thanks

You might find this 5DII CF Card Write Speed Chart helpful.

Pedro, the new version Extreme III cards transfer up to 30mb/sec (theoretically), and the Extreme IV (new black and silver version) transfer at 45mb/sec, but more importantly, Extreme IV cards are UDMA enabled. UDMA is important for the 5D2 because UDMA technology takes the transfer horsepower off of the host processor (in our case the 5D2), basically making everything go faster. Now, Canon states that a UDMA card is mandatory for video. However, many people have stated that they've used Extreme III cards for video, but that does put more strain on the 5D2. Some have stated that when using video the 5D2 gets very warm, and can even shut down. I'm 99% sure that those folks are using non-UDMA cards. Makes sense... if the 5D2 is doing the data churning, of course it's going to warm up. It's just best to get UDMA cards (also known as 300x cards in the Lexar world). I recently purchased three 8GB Extreme IVs at Adorama.com for a total of $90 after rebate. They're cheap enough now!

I have both cards in my 1DS III, I shoot landscapes mostly so I don't really have issues with write speed. However, downloading can be slow. I bought a Extreme IV card and the Sandisk CF reader made specifically for that card and it was easily 5 times faster downloading than the Extreme III card.

Thank you for your help guys!