The 360 on the dash is unbearable to me, it drowns out my raptor when sat on my desk on a mouse mat so the 360 is nothing to compare it to!
If you want a quiet case then it should be obvious that the less fans you need to use the better your case will be are running quietly, more fans means there will be more heat pockets when you turn one off by the rule of thumb.
More fans = more chance for vibration.
Throwing lots of CFM at a system can cool it well, very well in fact. However throwing a concentrated 5cfm at a component exactly as it requires can cool it just as well.
The best example I can possibly give from my first hand experience.
Cheiffy Scoprio full tower fitted with 6 80mm delta fans in total, 2400 cpu temp in the mid 40's. ATCs 500 armed with 2x Zalman 80mm low noise jobbies is givng me at 7v a almost silent rig with temperatures of low 40s idle and high 40s load.
The difference in noise is astonishing, the only real difference I have is my experience over the past 5 years of cooling computers and realising what they need to actually cool them.
The 900 no doubt is good for specialist systems, but it is too small and has too many fans for what I would consider average use.
Out of the two cases listed I would buy the Soprano as I consider it to be the superior case out of the Tsunami / Soprano.