The main difference that I can see right now is that GRZ has plenty of free cash and their bondholders are not a problem.. GRZ's convertable bonds can be paid back in cash or in shares at the company's option. They run until 2020 or there abouts and while there is a one day option to allow redemption in 2012 the holders would have to be prepared to accept shares and get no further interest payments. GRZ has the cash to pay the interest for a long time and fund all legal costs as well.
GRZ's claim is legally simpler than KRY's in that it was a straightforward concession which a permit had been granted for, and subsequently voided without cause. The fact that the permit had already been granted and GRZ was still prevented from building a mine is going to be hard to overcome by the Ven legal team.
Also GRZ has had sole access to all their data on Brisas and have kept it secure and I understand out of Venezuela. KRY's data was originally Placer Dome sourced and the CVG has all of that and probably has much, if not all of the later stuff as well. That makes bargaining for an early settlement much harder for KRY.
Providing that they can finance the action KRY will probably get an award from the ICSID but they have to keep the wolves at bay for long enough to wait out the delays and obstructions Ven will place in their path.
IMO KRY should have gone for arbitration much earlier, as time costs money and to complete the ICSID case will be expensive and drawn out. If they can fund it there could be a nice bonus for the patient shareholders unless they get diluted out by the need to raise funds, probably accompanied by a reverse split of some kind.