I'll just say from purely an aesthetic and flavor point of view I think the Primaris Marine looks better. The Smol Marines were nice and all but everything on 40k universe is huge and those large squads of Smol Marines end up feeling like they were some souped version of the Guardsman.

The new Chad Marine, being more expensive and bigger «feels» more in line with how the lore portraits them.

I'm sure I'll offend some 40k player with those comments though. :)