In term of cooling not much different.
Unless your house got more guest and some corner can't reach to 90% of cooling only.

Can I know your hall how big of overall size?

I can't said 2hp is good enough, may due to your actual condition, such as direct afternoon sun lah or 2 storey height at living hall.

How I know right.

Should be ok for 2hp.. not as too cold, still quite comfort level 

when to 2.5hp more strong airflow, more easily to reach some corner only.

Similar function in some other Ac brand too. Just disable, because it will increase temperature when detect less movement this will make the area warmer. Of you want fast cooling switch to powerful mode, will cold faster also eat higher current. Most inverter have this function too.

Econavi and inverter is totally 2 different front.

Econavi is detecting movement in the room hence adjust the cooling delivery, so some electricity can be saved, when not utilised.

Inverter is the ability to run motor at variable speed to save electricity.

Even Econavi is off, inverter saving still able to achieve through temperature setting. Just you have econavi to add on top oo it.

Fans always give noise when being run at high rpm, same with computer processor fan, chassic fan.  This is inevitable.
High rpm --> high noise.

Want quieter one, then need to run at low rpm, so the concept is always the same for all fan mechanism, that's why those computer cooling fan, when they want it to be quieter, they build it larger so that can run at low rpm with the same amount of output of airflow.

Have you do your monthly aircon cleaning?

Service? Please do self cleaning filter maintenance as often to avoid sticky dust on coil fins.

Panasonic still better choice, but Hitachi latest as sleep model maybe slightly better... which one is suit to you then go for it 

Durable or usage is depend how to keep clean or maintenance as often for empty dust on filter.