If you intend to do schutzhund you need a dog from working lines. The you showed does look like working lines.
The darker the dog there is sometimes a bigger intimidation factor. Of course there are a lot of factors including how the dog carries himself.
Male or female is up to you and your personal preference. I once trained a full brother and sister at the same time and my decoy once mentioned that my male would kill the bad guy and fling him at my feet as an offering where the girl would prob only render him unconsciousness but would hide the body well enough that no one would find it.
Before anyone takes that literally we didn't really kill anyone but we did enjoy seeing the difference in the two siblings and would spend some time discussing it! LOL
But, possible schutzhund, business security. How important are these traits to you? If it's real important you may be better off getting a slightly older dog that can be tested a bit.