Setting a variable assets field, depending on the URL? How can I set different assets fields depending on the URL?

I tried:

{% if craft.request.getSegment(1) == 'special' %}
   {% set assetfield = variantfield1 %}
{% endif %}

{% for asset in entry.assetfield %}     
     ...
{% endfor %} 


But that doen't change entry.assetfield?
I'd probably do it like so:

{% if craft.request.getSegment(1) == 'special' %}
    {% set assets = entry.assetfield_1 %}
{% else %}
    {% set assets = entry.assetfield_2 %}
{% endif %}

{% for asset in assets %}
    ...
{% endfor %}