No brainer.... go with the InSight.  The InSight has more expandibility.  It will do auto Steer, rate control, boom control, etc.  You can add an EZ-Boom or Direct Command etc. 

The AFS Pro 600 has some of the same capabilities, but you are pretty much married to red equipment with it.  The InSight will work in about any color.  I am not sure what file format the 600 is using.  At one time CNH was using a proprietary format and they were not very open with it.  It took a long time before they gave 3rd parties the ability to read it.  I don't know if they are still using their format or if they have adopted the AL format.  The 600 is proprietary hardware.  It is not a rebadged  InSight.

The 252/5100 is a high end receiver.  You can get by much cheaper if yield mapping is all you want to do.  If guidance is in your future, you might what the high end receiver.