The FTS (screening test) uses your blood tests and the scan to estimate the risk of some trisomy conditions including Downs’ syndrome, whereas the Harmony test looks at the DNA in your blood to see the number of copies of the chromosomes, hence, yes, it’s a more precise.. and it’s a lot more expensive.
Personally I did the FTS for both my pregnancies because the risk based on age was low, and I wasn’t in a hurry to find out the baby’s gender. Heh