The Japanese, previously Bridgestone's technical chief and now working with Ferrari on "tyre issues", is uniquely placed, having worked closely with both Schumacher and, now, Spaniard Alonso.
Having run away with the 2012 championship lead despite arguably not enjoying the best car this year, some commentators believe Alonso is among the best drivers of all time -- and perhaps even better than seven time world champion Schumacher at his peak.
Hamashima, better known in the paddock as 'Hammy', was quoted at the Hungaroring by Spanish news agency EFE as saying Schumacher and Alonso are "so very similar".
"They never give up in their efforts to achieve victories and titles," he said.
"I think Fernando is calmer and Michael (is) more aggressive," added Hamashima.
"In meetings, Fernando says the right thing, and calmly. Schumacher also made good comments but his manner of expression was different," he added.