BQM 442

what is Blacks best move?  

In 7x7 Go b is mentioned as best move. While on an SGF about the same problem a is given as best move.

Please high ranking Go players tell me (12 kyu) what is best.

The throw-in  

Dieter: I am no expert, but here's what I see. Black's throw in forces an extra move inside White's territory later.

 

If White inadvertently covers the neutral points, Black has the tesuji of to create seki.

Simple descent  

If Black simply descends, White gains a point with . So I'm inclined to vote for the throw-in.

Ko  

White has a countermeasure though. So, I must think again.

Tromps Continuation (2) 3 at , 21 at  

your remark about the neutral points is valid white needs to add a stone inside his territory so loses a point under territory rules (and this way the problem becomes an wholeboard endgame problem