Resurrecting another OLD thread...
I have been a long time user of Sidi Boots. My Vertabra boots have been thru a couple of lowsides with minimal damage. They seem to have good sole/toe wear and stay together. The ankle armor and support is a big plus too.
Last year I picked up a pair of Alpinestars SMXs because I came across a good deal. I decided to wear them for all my street adventures. Fit is good with ample protection, but build quality is not up tp Sidi's level. Some stitching that is not stressed has broken or maybe the leather was pressed too hard and cut during manufacture. Regardless, they are not holding up very well. I am disappointed in these A*s because I think they make a fairly good quality set of leathers and gloves.
I just picked up a barely used pair of Sidi Corsa Air boots and look forward to testing the ventilation of these.