Compare Value to Category Title In Template
Your entry_pos is an Element Criteria Model. You want to get the first (and probably only) category from this ElementCriteriaModel, and then compare its title to 'staff':

{% set entry_pos = entry.position.first %}
{% if entry_pos.title == 'staff' %}
  ...
{% endif %}


This will give you an error if there is no entry.position.first, as entry_pos will be null, so you should defend against that somehow. One possility is:

{% if entry_pos and entry_pos.title == 'staff' %} ...


Another is to use twigs useful null-coalescing operator:

{% if (entry_pos.title ?? '') == 'staff' %} ...


With Craft 3, you will use one instead of first, but otherwise everything is the same.