Given a student coming to the end of their undergraduate career working on both a thesis for their bachelor degree as well as a separate research project in a research lab, which would hold more weight towards graduate admissions in US schools.
The main questions started with; in admissions, do people read the bachelor thesis.
I never have, but can't be sure of a standard. If the student is working on a research topic that is set to be submitted for publication, should they focus on that paper and not worry about the bachelor thesis, vice versa, assuming time is constant and the bachelor grade remains the same.
My first thoughts were, a bachelor thesis is not peer reviewed, so any peer reviewed article would be much more likely to be read or at least glanced over beyond the title. No one expects much out of a bachelor thesis, so it will be hard to convince someone to read it, maybe without some two page overview summary linked to the application.