Probably because your sizes both have the same width, and you have it set to “proportional crop”, which won’t necessarily crop to your exact dimensions. (See the Codex)
In all likelihood, it is actually creating both images–but they’re both the exact same size, so one overwrites the other 🙂
Try changing the last param to “true”.
add_image_size( 'featured1', 466, 316, true);
add_image_size( 'featured2', 466, 260, true);