I'm not that familiar with japanese trains tbh, but from what I've read they seem to have some pretty neat ones. Shinkansen looks fucking futuristic.
When it comes to high speed train my heart has always been with the German ICE-trains though, the third generation also tops over 300km/h but the older ones are my favorites. Lots to do with them being featured in old Märklin-cataloges and all.
But heavy as fuck cargo trains are still cooler, there is something special about multiples of really strong locos crawling up through the mountains with a trail of cars that appears to never end after them.