I have the 177 which is a 179 without temperature and a 189 which is one step up from the 187 which is the replacement for the 87. The 177/179 is 6000counts and .09% accuracy. The 87 is 20,000 counts and .05% accuracy. The 187/189 is 50,000 counts and .025% accuracy.
The 179 is about $200, the 87 (series III) is about $350 and the 189 is around $400.
In the field, I prefer the 177/179 since the accuracy is more than enough and they are smaller. With the money you save, you can get a clamp on AC/DC ammeter like the 380947 400A meter from Extech:
http://www.omnicontrols.net/x380942.pdf
It really helps trace down problems with poor connections in multiple strings without removing any wires.