After suffering with hurting, burning feet that felt like they were being squashed, for years, I gave up my red Sidis for Shimanos. My feet are not wide, and I wear a small size, but I have a bunion on one foot and I just can't tolerate anything tight. The Shimanos have a wide toe box, and I got the ones that are molded to your feet. I had to wear 2 sizes larger than my street shoes in Sidi, and i was able to go down one size in my Shimanos. I still keep the ratchet pretty loose, as well as the straps, but that's me.
Another thing that has helped me immensely is wearing very thin wool socks all year round. It has virtually eliminated the pain in all my sporting endeavors. And I bought Mizuno running shoes that have a wider, meshy toe box area, but still have support in the heel.