Modifying protexted picture sizes: use "add_image_size()" or "update_option()"?

I am discovering conflicting information on whether or not it is okay to override protected WordPress picture sizes (thumbnail, medium, medium_large, and enormous) with add_image_size(). Some docs point out it is higher to do that with update_option (). Is there a sensible distinction between these units of code:

perform mytheme_image_sizes() {
  add_image_size('thumbnail', 200, 200, true);    
  add_image_size('medium', 480, 480, true); 
}

vs

perform mytheme_image_sizes() {
  update_option( 'thumbnail_size_w', 200 );
  update_option( 'thumbnail_size_h', 200 );
  update_option( 'thumbnail_crop', 1 );
  update_option( 'medium_size_w', 480 );
  update_option( 'medium_size_h', 480 );
  update_option( 'medium_crop', 1 );
}

Be aware: I am specifying these in my theme to cease admins from arbitrarily altering sizes and screwing up the post-4.4 responsive pictures perform, and I am going to most likely take away the admin interface to vary the picture sizes.