I believe its a combination of both. Both these types of skills take time to develop so I would recommend you keep balance. I have seen people with great technical knowledge and skills lack basic soft skills like communication and presentation skills. Also I have seen people with great soft skills struggling to compete with those with great technical skills. So my suggestion would be to balance both.
These are some of the skills that researchers must develop.
https://www.enago.com/academy/transferable-skills-that-phd-students-postdocs-must-develop/