Does 30mb/60mb really matter in compact flash card?

I plan on buying some backup cards and I want to get a san disk 8 30/mb a sec card to do weddings? Does it matter if I get a 30/mb a sec or 60/mb a sec? Thanks in advance.

Your 5DmkII surpports the UDMA capacity of the 60mbs cards. You'll notice a difference in the number of photos you can take consecutively using the 30mbs card. If you use FW800 you'll also want the 60mbs cards to transfer the files over.

I use the 30mbs cards for my 40Ds since they don't support UDMA. However in my 50D I use the 60mbs cards and it makes a difference in how I shoot. I can buffer out several times each day I shoot, but then agian I shoot sports/races. When you need to get one shot of everyone crossing the finish line, it gives me more of a ability to do so.

ZXDrew wrote in post #11868285
Your 5DmkII surpports the UDMA capacity of the 60mbs cards. You'll notice a difference in the number of photos you can take consecutively using the 30mbs card. If you use FW800 you'll also want the 60mbs cards to transfer the files over.

I use the 30mbs cards for my 40Ds since they don't support UDMA. However in my 50D I use the 60mbs cards and it makes a difference in how I shoot. I can buffer out several times each day I shoot, but then agian I shoot sports/races. When you need to get one shot of everyone crossing the finish line, it gives me more of a ability to do so.

I was thinking that is what it affected. Thanks again.