I went through the exact same comparison a year and a half ago (when it was still the SMX-5). I really liked the Sidis, but I ended up getting a good deal on the Alpinestars. I've worn the Alpinestars at several track days, and wear them quite often when I'm riding through town and on backroads. I have no issues walking in them at all, and I absolutely love them. If my SMX-5s ever wear out, I'm going straight to the SMX-6. The Alpinestars are definitely a great choice for street use with occasional track duty.