The A1200's onboard IDE is only PIO mode 0 (programmed input/output) with a theoretical maximum of 3.3MB/s throughput... as bloodline said, in reality 2.0MB/s is more likely.
You can get CF cards that will happily do 20 - 30 MB/s.
The latest SATA 3 drives have a theoretical 6000MB/s throughput... 2000 times faster than what the A1200's IDE controller can provide.
I think you can get a FastATA accelerator for the A1200 which offers faster PIO modes but even they only go up to 16MB/s. Still slower than what a CF card can handle.
So essentially you'll be throwing a lot of money at this, for an SSD, a SATA-IDE adapter and perhaps a FastATA, and the system will be no faster than if you'd used a CF card.
The CF card isn't what's holding you back, its the IDE interface in the Amiga.