So we're converging on a Mitsubishi Multi-split system probably the 10.2kW device (max 5 indoor devices) - MXZ-5F102VF because it's the most energy efficient, uses R32, and quietest indoor units. The question is about those indoor thing

 

In the one corner, we have the ducted (hidden in ceiling)   SEZ-M R32   (page 66) - in particular the 2.5kW SEZ-M25DA, featuring:

- Airflow (medium) 117l/s, 25dB

- Efficiency: SCOP: 3.80 SEER:5,30 ErP class A

 

In the other, we have the MSZ-LN R32 (page 20) - in particular the 2.5kW MSZ-LN25VG2 

- Airflow (medium): 118l/s, 29dB

- Efficiency: SCOP: 5.2 SEER: 10.5 ErP class A+++

 

The 'in ceiling' one of course is a lot harder to install smoothly, but certainly doable. I guess I prefer the in-ceiling for aesthetics but the on-wall are OK too. The crucial part is the efficiency vs the noise.

 

Efficiency: Sigh. How can one be A and the other A+++ ? Aren't they both just a cleverly shaped coolant expansion tube? And why does the selected outdoor unit much more relevant to the efficiency rating at the end of the day?

 

Noise: both are fairly quiet but the ducted one  is literally more than twice as quiet still. Eh. 

 

To save you some rummaging through the PDF I'll attach the images below.

Update - I think I'm starting to figure it out - the ratings are "sometimes" (man this flyer is confusing) based on some random indoor device with a random outdoor device paired. So they just picked different devices for the different indoor units, wildly varying the final rating of two comparable units.

 

Instead i think both efficiency ratings are somewhat close. OK - that makes that choice a lot easier. Or am I mistaken?