Shop promoter a lot of time has vested interest. They just want to sell.
Want to sell A brand time, say B brand no good, A better choice.
Want to sell B brand time, say A brand no good, B better choice.

Installer know more about aircond than those shop promoter because of hand on installing.
Better ask installer, as whether A or B brand, they still charge the same fee, hence they are more neutral in comment.

Blowing fan upwards meaning?

to not get the cool wind from the AC directly to you