I've proper wide feet and wear Lake, go on their website for a detailed breakdown on how to measure your feet.
Sidi are pretty slim fitting from what I've read, top quality admittedly but no use if they're too tight.
The 'wide' version of Lake's shoes offer 15mm extra width in the actual shoe whereas a lot of so-called wide fitting shoes simply let the foot 'spill' over the same size sole if that makes sense?
I spent ages reading up on wide shoes before making a choice, not all the Lake range come in half sizes either, I've settled on CX238's but they do a MTB version as well.
Top quality stuff mind.