A Matlab/Octave example of inv being slower and less accurate:<p><pre><code>  &#62;&#62; A = randn(100); x = randn(100,1); b = A*x;
  &#62;&#62; tic; x1 = inv(A)*b; toc
  Elapsed time is 0.142381 seconds.
  &#62;&#62; tic; x2 = A\b; toc     
  Elapsed time is 0.000736 seconds.
  &#62;&#62; max(abs(x-x1))
  ans =
     7.1054e-14
  &#62;&#62; max(abs(x-x2))
  ans =
     4.8406e-14
</code></pre>
Edit: Actually this is a warning about timing stuff. The inv function hadn't "warmed up". On a second run both times drop, and the difference is much smaller:<p><pre><code>  &#62;&#62; tic; x1 = inv(A)*b; toc
  Elapsed time is 0.000737 seconds.
  &#62;&#62; tic; x2 = A\b; toc
  Elapsed time is 0.000471 seconds.</code></pre>