Evaluate often gets misunderstood by students as compare. They're not the same. Comparing just points out similarities and differences; evaluation requires a judgment about which theory, application, approach, etc., is superior and why. Students working under time pressure are most likely to forget to write out their criteria for making the judgment in the first place. This rationale is often crucial for understanding the overall judgment.
Writing tip: Especially when you're pressed for time, keep the criteria obvious and straightforward. If one approach is cheaper and faster, and those are the two criteria anyone would use to evaluate the approaches in question, then talk about what makes one cheaper and faster. Don't forget, though, to also show what makes the alternative approaches more expensive and slower. Thoroughness does count when writing out evaluations.
If the obvious criteria are not appropriate in a specific context, though, be sure to explain why you're adopting not-so-obvious criteria for evaluating. So long as you can justify the criteria you choose and the final judgment you make, you're meeting the goals of the essay question that calls for evaluation.
Substitute key words: rank, order, justify your selection, explain your rationale for choosing