Although I can't speak for the other straps you are considering, I do own the Silva straps. I upgraded from some cheap non-laminated straps and, obviously, the Silva's are far better. I don't ride brakeless, but rarely use my brake and these straps are quite sufficient. Under extreme tension (emergency braking), they do loosen up a slight bit. However, I suspect that some other laminated straps of comparable price may do the same.

One a side note, does anyone know if Freewheel ships? I want a set of the Gucci double strap holders.