While both watches are GMTs, they perfectly illustrate the diverging paths that Grand Seiko takes its GMT offering. The Hi-Beat watch (ref. SBGJ277) is made in stainless steel, with a case measuring 44.2mm by 14.8mm thick, housing a 9S86 movement 
link running at 36,000 vph. 
link Conversely, the high-intensity titanium 44.5mm 
link by 14.9mm case of the Spring Drive GMT (ref. SBGE307) houses the highly accurate 9R66 Spring Drive movement that runs ±1 second per day / ±15 seconds per month on average.