I found renting a car in Calangute quite convenient when I visited Goa because I didn't have to depend on taxis every time I wanted to go somewhere. I was staying around Calangute, and having a car made it much easier to visit places like Baga, Anjuna, Candolim and even some quieter spots.
One thing I learned, though, is to check the rental terms properly before taking the car. I initially focused only on the daily price and almost missed checking the fuel policy and insurance details.
If you're flying into Goa, you can also look at car rental options available through Manohar International Airport, especially if you want to pick up a car soon after landing. For me, having the car from the beginning made the trip feel much less rushed and gave me more flexibility with timings.