ive used one before, terrible to work on a pc, always had driver issues with it, solid on the mac tho, so maybe think about that too depending on what OS you have.
sound wise, i cant say ne er using the focusrite, but if i had to pick between the two. id go focusrite, knowing how much of a pain the tascam can be on a pc, (if that counts) know someone who had one die on them too. and focusrite have very solid driver performance and ive read good things bout the us122. News - Press Release: Focusrite Announce Scarlett 2i2