Local Nagasaki TV station had a report on Nagasaki Marriott, they had the open house for the press before the ground opening. The video is in Japanese but has a lot of images of the hotel.

It looks from the video that Nagasaki Marriott went one step above Hilton Nagasaki. The TV report said 70% of guest rooms have a balcony. The top room, Imperial Suite has a published rate of 550,000 yen/night (US$ 3,747/night, € 3 447/night) The second guest room shown after the Imperial Suite is Premium 2 Balcony Double Room.

The hotel website says the Standard room (2 double) and Delux room (1 king) have a city view, and the Premium Balcony room has a Harbor/Mountain view. All these rooms are 36 sq meters/387 sq. feet. It could be that all these rooms may be the same inside of the room, the difference could be the view from the room.

Comparing Hilton Nagasaki and Marriott Nagasaki a little more.
Breakfast buffet: 5500 yen at Marriott (3800 yen at Hilton)
Weekday lunch: 5500 yen (three-course prefix) at Marriott (3500 yen lunch buffet at Hilton)
Sushi dinner: Omakase 17600 yen (12000-25000 yen course meal at Hilton)

Doing Omakase means Marriott Nagasaki is targeting non-Japanese visitors.