How to sort posts by two dates

I have two post types I want to list together: News and Events. Events displays an ACF date and News displays the wordpress publish date. I would like an event that occurs in the future to appear above a News item that has already been published. For example:

EVENT
June 6th, 2016
Name of Event

NEWS
January 2nd, 2016
Headline

This is the code I am using to display this. I just need to modify it to sort by event-start-date if present otherwise default to post date.

<?php $queryArgs = array(
			'post_type'      => 'portfolio',
			'meta_key'		 => 'post_views_count',
			'orderby'		 => 'meta_value_num',
			'order'			 => 'DESC',
            'posts_per_page' => $postcount
        );	

		$query = new WP_Query($queryArgs);
		if( $query->have_posts())
		{
			while ($query->have_posts())
			{
				$query->the_post();
				?>

<span class="cat"><?php PrintTerms(get_the_terms( get_the_ID(), 'skill-type' ), ', '); ?></span><br />
<a href="<?php the_permalink(); ?>">
<?php if( get_field('event_start_date') ): ?>
<?php $startDate = DateTime::createFromFormat('Ymd', get_field('event_start_date')); ?>
<span class="counter"><?php echo $startDate->format('F'); ?> <?php echo $startDate->format('jS'); ?>
<?php if( get_field('event_end_date') ): ?>
<?php $endDate = DateTime::createFromFormat('Ymd', get_field('event_end_date')); ?>
- <?php echo $endDate->format('jS'); ?>, <?php echo $endDate->format('Y'); ?></span>
<?php else : ?>
, <?php echo $endDate->format('Y'); ?></span>
<?php endif; ?>
<br />
<?php else : ?>
<span class="counter"><?php the_date(); ?></span><br />
<?php endif; ?>
<span class="title"><?php the_title(); ?></span><br />
</a>
</div>
<?php
		}
}
?>