Including conditional logic in a custom template

Thanks again for helping me with the user avatar issue. I was going to ask another question there but thought it would be better to open another thread.

So, can we have conditional logic in the custom template? Let’s say I want to display the post thumbnail OR the user avatar if the post doesn’t have a featured image.

This is not really a question since I figured it out (I guess):

  if ( has_post_thumbnail( $post_id ) ) {
    $lcp_display_output .= $this->get_thumbnail($post);
  }
  else {
    $lcp_display_output .= get_avatar( get_the_author_meta( 'ID' ), 150 );
  }

Is there any cons to using conditional logic in the custom template? Does this significantly affects performance?

Thanks.