Controlled residential ventilation in insulated attic or basement?

At the moment, the ventilation system is being planned with us, and it concerns the exact location.

The technical room is already occupied for the heat pump, water, and electricity. There would still be space in the utility room, but the pipes would then have to go through the wall into the unheated basement and from there again through the wall to the outside.

The installer has now suggested going up to the attic and venting through the roof. The attic is insulated with wood fiber boards up to the ridge, as is the ceiling from the top floor to the attic.

What do you think would be the better solution and why?

A Wolf CWL400 is planned. I wonder if a cheaper CWL300 would also be sufficient? According to the installer, it would then always run at full load.

Use the CWL400 if you want to save operating costs.

Use the basement if you want to avoid moisture damage or installation costs.

Just install the system in the utility cellar just below the ceiling, then it will fit.

My HAR is 4.5 sqm and includes: Controlled residential ventilation (CWL 300), gas boiler + 300L storage tank and solar station, washing machine + dryer, network stuff, electrical system, and heating circuit distributor.

müssten die Rohre dann durch die Wand in den unbeheizten Keller und von da aus nochmal durch die Wand nach draußen gelegt werden.

Really bad idea, condensate is inevitable.

The roof is also rather suboptimal due to possible condensate damage. Sure, you can insulate everything (device + pipes) separately, etc., but those are costs which, IMHO, are unnecessary.