Display thumbnail based on upload size

Hello,
I’m using the wordpress thumbnail and would like to display different size based on upload size. I have two settings on functions.php:

add_image_size( 'Major story img', 1400, 700, true);
add_image_size( 'Old 575', 575, 300, true);

What I would like to accomplish on single.php is if an image upload fits the dimensions of ‘Major story img’, it shows that image. If an image does not fit ‘Major story img’ but fits ‘Old 575’, it shows the ‘Old 575’ image instead.

Thanks,
Gregory S.