Replacing Tamron 17-50 by 18-70 or Sigma 18-50 macro?

My Tamron 17-50 F2.8 has the below problems:

• overexposure in flash photos;

• occasionally mis-focus;

• strong field curvature (making objects at both sides blurred)

I am going to replace it by either the Nikkor 18-70 or the Sigma 18-50 F2.8 macro.

If you were I, which will you choose?

Rgds,
Edmond