First off, they are 2 different animals.
The Focusrite is a fairly plain and simple "dial it in and go" unit for me.
I like having the inputs on the front panel too!
I use the compressor sparingly if at all unless going direct w/bass guitar.
The mid-scoop eq control has been nice for my own voice and
the sE2200-A.
The ART is a little more complex with a lot of variey.
It can be real clean or real tooby and anywhere in between plus it has the plate voltage and input impedance controls that can alter sounds as well.
If I need compression, I just patch in the VLA.
I wish I had one more Focusrite just to have 2 channels worth.
However, my wish list includes a lot more than that
B