A different boundary, not a quality ranking
Indirect heating transfers energy across a heat-transfer surface. Direct steam contact adds a material interaction and commonly introduces a different downstream cooling or separation arrangement. The useful comparison is which path lets the experiment answer its defined product-quality question. Neither approach is universally better.
Keep the comparison interpretable
Document the formulation, feed condition, actual thermal history, flow, pressure and collection method. Differences in shear, surface contact, steam addition and removal, or cooling can affect the result. Changing the heating path while ignoring those differences can turn a nominal temperature comparison into several uncontrolled changes.
Ask for the proposed arrangement
The configurations available for a project must be confirmed in the supply proposal; this comparison is not a claim that every heating form is offered. Request a flow diagram and utility schedule. A direct-contact route also needs a material reconciliation beyond the simple once-through sample planner, which assumes no steam addition, evaporation or recycle.