Thule Aion 28 or 40?

I am pretty much set on the Aion but still self-debating the size.

I think I might occasionally have use for the extra space of the 40l. But most of the time I don‘t. How much deadweight does it carry (sloppyness of empty compartments, bulky look…?).

On some of the promo photos it does look quite substantial, but then models tend to be of a more svelte build so it might cheat the eye. In some of the youtube reviews it seemed reasonably compact.

Long story short: what did you go with and is there anything that makes you wish you picked the other? Thanks!