I've just done this, and used the same conditional as on the facebook like...as they will only want to show together. May be a bit simplistic but works perfectly.
Code:
<vb:if condition="$show['fb_likebutton']">
{vb:raw fblikebutton}
</vb:if>
<vb:if condition="$show['fb_likebutton']">
<a href="https://twitter.com/share" class="twitter-share-button" data-via="LegalBeagles">Tweet</a>
<script>!function(d,s,id){var js,fjs=d.getElementsByTagName(s)[0],p=/^http:/.test(d.location)?'http':'https';if(!d.getElementById(id)){js=d.createElement(s);js.id=id;js.src=p+'://platform.twitter.com/widgets.js';fjs.parentNode.insertBefore(js,fjs);}}(document, 'script', 'twitter-wjs');</script>
</vb:if>