I have seven GBoxes and one VBox (oink-oink). Operationally all have been reliable. As was pointed out, the VBox costs less.
The chief difference between them is in how they count the signals coming back from the positioners. All the HH motors and actuators I own send back a reasonably symmetric square wave. In other words, the "on" pulse lasts about as long as the "off" pulse. A VBox counts one cycle (one "on" plus one "off"), whereas the GBox counts edges (each pulse, whether "on" or "off"). Thus for the same dish movement, a GBox will show twice as many counts. For a symmetric square wave, this effectively improves the resolution of the positioner by a factor of two (ie. provides smaller steps). If you happen to have a positioner with a highly asymmetric return signal, there would be little improvement.
I used the term resolution instead of accuracy, because they are rarely the same. More resolution should never hurt, but it may not always help. If you have a very large dish for the intended band (C or Ku), a better resolution can provide a better peak position, particularly with positioners that have large step sizes. But if the steps are already small, it may not make much difference. There are other issues that come into play if the dish has mechanical slop, or if the positioner has backlash. In those cases the dish positioning may not be repeatable even when the controller indicates the same count. Still, you can manually tweak if you're willing.
GBoxes feature four-digit counts, while the VBoxes have only three. That could make a difference if you have high-count positioners. But all of my positioners would work with either, partly because the VBox counts at half the rate.
I've had to open several GBoxes after receiving them because they were poorly packed and/or abused during shipping. The internal construction did not impress me. In two of the cases, the rather heavy transformers had broken off their mounts and were bouncing around inside. In one of these cases, this split two of the circuit boards, breaking a number of the traces. I fixed this because I hate arguing over returns. I have not opened my VBox, although it "feels" better when I give it a "shake test", compared to a GBox. Both have pathetically flimsy contact posts in the back, although the VBox looks like it would last longer.
