Looking to buy 2 X 16GB SDHC.

Whats the difference between

SanDisk SD/SDHC (Extreme III class 6 30mb/sec)
Without packing (plastic case and memory card)
1GB= RM33
2GB= RM42
4GB - RM59
8GB - RM119
16GB= RM154
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*NOTE: Price exclude shipping

and

SanDisk SD/SDHC (Extreme class 10 30mb/sec)
without packing (plastic case and memory card)
4GB - RM79 (Cass10)
8GB - RM155 (Cass10)
16GB - RM299 (Cass10)
16GB - RM319 (Class 10, With retail packing)
32GB - RM399 (Cass10)
*Note: Free Shipping by pos laju, add RM3 for insurrance (Optional)

Both are 30mb/sec but 1 is class 6 and the other is class 10. Are the speed same for both? I might get the cheaper 1 unless I'm missing something?