Sidi Mega

[hainy]

I have Genius 5 (44) black, Ergo 4 (44) white. Both are Mega and I am sure Genius pair are more confortable because they are a bit wider. Are the ergo's generally not as wide in Mega.

[Plum Hill]

It would probably depend on how the last is designed.
Sidis are definitely handmade, so fit varies. Years ago I tried on three pairs of the same size. All fit differently.
This summer I ordered a pair of MTB shoes, 44 Mega, same as my road shoes. Fit was tight. Found a pair on the dust-covered top shelf in a bike shop, tried them on, and was happy with the fit. Size: 44 Mega.

[vqdriver]

didn't know they were handmade, but my experience echos the same. i wear a 43 mega in genius 6.6 and 43 mega in whatever mtb shoe this is. the genius is a bit wider in comparison.