I would definitely recommend the Focusrite over the Tascam. Focusrite has better preamps to my ears and if you get the 18i20 you also get access to Mix Control which not only makes the interface VERY customizable, it allows you to configure it for offline mode as well.
I currently have 3 Focusrite interfaces: Solo, 2i2, and 18i20, depending on where I am working. My 18i20 is paired with a Focusrite OctoPre for 16 channels in and a Behringer ADA8200 for 20 channels out.