CF cards (and other removable media, even flash drives) don't have nearly the performance of an SSD or even a HDD. The random performance may be competitive but the majority of I/O on a client machine is sequential (although the most time on an HDD system is spent on random I/O).
Most CF cards have a typical peak sequential read/write speed of < 90 MB/s. Compare that to a recent SSD with read/write speeds of 200-500 MB/s. There is simply no contest. A cheap 64 GB SSD would easily be more cost effective and better performing than a CF and SATA adapter.