From the pictures in the actual GW promo video, it appears that the Primaris stands a head taller than its older Space Marine counterparts. Check out actual video of the Primaris below:
It's appropriate that we finally will have realistic scale Space Marines that tower over regular humans (the marines are supposed to average around eight feet tall). The current marines in their weird Space Marine squat pose stand just as tall as regular human Imperial Guardsmen.
Here's a picture of the current squatty Space Marine below:
The official GW site states that:
"The Primaris Space Marine is a new breed of hero for this, the darkest age in the Imperium’s history. These new warriors are the next step in the evolution of the Emperor’s Angels of Death – genetically altered from their brethren to be bigger, stronger and faster – timely reinforcements to the Imperium’s armies as their enemies close in for the kill."
Here's a screenshot of the new Primaris from the video.
"Any of the galaxy’s many hundreds of Codex Chapters can use Primaris Space Marines, along with many of the less Codex-compliant ones like Dark Angels, Blood Angels and Space Wolves."
I can't wait for the Primaris release, possibly next month... Thanks for the read!