The Hattori and Massamoto are very nice knives. You can't go wrong with either. The Massamoto easily takes a very keen edge. The Hattori gets very sharp, with little effort. The Massamoto seems to get a little sharper, but the Hattori is no slouch. The Massamoto is light and agile. The Hattori has a little more heft. From what I've seen of the Hattori line, the knifes are nice compromise between thin lasers, and thicker work horses. The handle on the Hattori is one of the best on a production knife.
If you are only going to buy one Suji. I'd go with the Hattori. I use mine to cut up a lot of fruit, so I appreciate it being stainless. A good handle makes a knife all that more functional, and the Hattori has one of the best.
Good luck with you decision.