On Mon, 27 May 2013 11:20:33 -0700 (PDT), Jim K
wrote:

mmm try fixing something worth fixing to the concrete with both types
and share the results?

I;d expect the proper (massively overpriced) concrete screws to cut a
better sharper thread in the concrete and so grip better than a forced
in coach bolt - that, I;d expect, got worn out & mangled during the
"pneumatic impact hammering" stage...

Possibly, but the function of the bigger bolts is to take some of the
shear load on their shoulders (it's a wall plate with a dozen joist
hangers). Each larger bolt is neighboured by two smaller ones, which
are cheap as chips and a piece of **** to drive in. So, there's no
shortage of load-sharing and plenty of strength in the assembly as a
whole. I just object to paying through the nose to a supplier who
thinks they can charge what they like for stuff like this.