Unless the cloud is overloaded, there should not be much difference. In case of doubt, just run a given program on both your personal computer and the cloud and use %timeit my_sage_command so see how long it takes in both cases. Anyway, the main rule of project Euler is that the solution should not last more than one minute on a modest computer, so it is lilely your student's programs are not optimal
Unless the cloud is overloaded, there should not be so much difference. In case of doubt, just run a given program on both your personal computer and the cloud and use %timeit my_sage_command so see how long it takes in both cases. Anyway, the main rule of project Euler is that the solution should not last more than one minute on a modest computer, so it is lilely your student's programs are not optimal