USB 1.1 provides a theoretical throughput of 12mb/s
CF has a bandwidth of 16 mb/s IIRC (I'm to lazy to look this up atm)
ATA-133 provides a theoretical throughput of 133 mb/s
What numbers are larger?
There are arguments about the benifits of no seek times with CF, but I don't buy it. It is also noteworthy that CF cards wear out far sooner then a hard drive.

and draw your own conclusions.