Is it better to have a less personal recommendation from someone with high authority, or a more personal recommendation from someone with a lower position?
I agree that both can be helpful. Where possible, though, give yourself some time to build a relationship with someone you might consider "less personal" and that is of "high authority". This person of "high authority"...maybe reach out to them to ask for a little time. Maybe you can attend a (virtual) talk that they are giving.
In general, a "personal" recommendation or letters of recommendation are so much more impactful both in the ask and in the letter provided, when you, in fact, have a good, authentic relationship. It is impactful in the ask because often times the person who you ask for the recommendation is honored that you chose them. It is impactful in the letter provided because you get to hear from others how highly they think of you and/or how much they recommend you for a position or task.
I hope you find this response helpful.
Best of luck!
It's actually a good idea to have both. But if you only secure one, it's better to secure the professional recommendation over the personal recommendation. My letters of recommendation included 1 from a teacher, one from my boss at my internship/job/volunteer work; and one from a family friend.