The most interesting physical difference is the the height of the two men with Hasegawa having an amazing 7.5CM (3") height advantage. The Japanese fight couples this with a reach advantage, albeit a less significant one.
Martinez is physically imposing however and has a much thicker chest, something that could be used to explain why the reach, or rather wingspan, of the two men is closer than we'd have expected.
Whilst Martinez is naturally taller and rangier his key advantage isn't a physical one but is instead based around his experience. He has fought in more bouts in general and 7 times more world title fights, a major edge at this level. He is however 5 years older than Martinez and will be fighting in his first world title fight for 3 years.