Each of these strategies has very different objectives.
The first one will be very short-term with a lifespan of only a few months. This is an excellent strategy to generate cash flow quickly.
The second strategy demands more work. It is often necessary to create its branding, take care of the site, optimize each stage, build a relationship with the customer... But it's often a much more profitable strategy in the long run.
No method is better than the other.
As cash flow products can be used to fuel the launch of a single-product store, these are two strategies that can be used simultaneously.