Partial hydrolysis of XeF6
Both can be formed. It depends on the amount of water added: 
\begin{align}
&amp;&amp;\ce{XeF6 + H2O  &amp;-&gt;  XeOF4 + 2HF}\\
&amp;\text{or}&amp;
\ce{XeF6 + 2H2O &amp;-&gt; XeO2F2 + 4HF}\\
&amp;\text{or even}&amp;
\ce{XeF6 + 3H2O &amp;-&gt; XeO3 + 6HF}
\end{align}