If this is a continuous data logging system then definitely do not use an SD card because it will fail very quickly.
Define "quickly".
And support your argument with hard data.
Throw out some numbers...
Use a 2GB SD card. Keep it SD vs SDHC for simplicity on the firmware side of things.
4 bytes @ 30us = ~133 1/3 KBPS, call it 150KBPS to keep the math simpler.
10 minutes of 150KBPS = 90 MB, call it 100MB, again, keep the math simple.
2GB card, ~2000MB (maybe the card ain't so great and has bad spots, whatever works).
2000 MB / 100 MB = 20 data dumps before the card is full
20 data dumps * 10 minutes = 200 minutes, simple math, call it 3 hours.
About an average of 100,000 write cycle endurance for a good quality SD card. Call it 10,000 write cycle endurance, even with wear leveling that most decent SD manufacturers have in there.
10,000 * 3 hours = 30,000 hours = 1250 days of continuous writes/over-writes = ~3.4 years.
How quickly will it fail again?