I just arrived on Easter Island yesterday. Haven't rented a car yet, though I might tomorrow or the following day. The lady who runs the place I am staying said Oceania is the cheapest car rental place in town.
I hiked up to Orongo this morning. Since I love hiking and since the max elevation gain is something like 300m or 1000ft it is not a hard hike. You can hitch a ride back to town but I took a different route back walking.
The car rental will give you flexibility. But if you are just looking for a beach, you can find that a lot closer than Easter Island. The main reason I might not rent a car is that I am looking at doing one-way hikes and having a car would be an impediment. So I might just take a taxi.