I picked up a 12 inch long anti siphon sillcock at the store today. It is one of those 1/4 turn ones.

I notice the threaded supply side has quite a narrow opening as does the hose connection end.

It has some sort of little spring loaded poppet valve on the supply end. I am guessing the actual shutoff valve is beyond the poppet since turning the handle has no visible affect on the poppet.

I have 3/4" copper lines going to it.

But now I am wondering if the flow rate on these things is severely choked because of the design?

Would I be better off, as far as flow rates, with just a shutoff valve installed a foot inside the house and a thread on vacuum break outside mounted on a regular water valve with a larger opening?