It would be down to the individual to decide whether a particular result is good enough for them. You can use the retroactive smoothing slider in the shape editor tool to remove some of the rough edges in the Xara traces, but that's more work. I am interested in the Inkscape tracer now you've brought it to my attention. I wasn't able to reproduce your result however. To help me, please could you attach the exact image file you used for the trace above along with screenshots of the settings used in Inkscape's tracer? Thanks.