Gravel is easier to clean in terms of concentration as you just stick the vac in the gravel but sand is easier (after a bit of practice) as long as you can hold the vac above the sand as all the gunk will rest on the top of the sand.
Sand you will need to stir every now and then or get snails like
MTS that will dig around in the sand to mix it up.
Looks, that's totally personal opinion but i think sand looks better.
It is also easier to plant roots in sand then larger gravel, smaller gravel probably is just as easy as sand though.