It is certainly easier and more comfortable to through your suitcases and other travel gear in the trunk than dragging them on the train or bus. Been there done that. Trust me - I know.
Your day to day life is is all about being on time and following a fixed schedule. Do you really want to be on a schedule when you are on holiday? I don't. Not to mention that if you drive you will have access to places public transport doesn't go to. Wait! You want to stop on the side of the road to take pictures of the beautiful landscape? You can't ask the bus driver to stop the bus for you...
3. STRESS LESS
When using public transport you have to make sure you are in the station on time, you have to carefully calculate all your activities and how much time you allocate for each of them. You should relax and do what you feel like doing not what is in the diary. Maybe you suddenly decide to pack your things and go to a different beach, maybe you want to sleep more in the morning. Don't stress with all that planning. Be spontaneous without hassle.
4. SAVE MONEY
Renting a car turns out to be the cheaper option especially for group travel. On our family holidays my dad always rents a car to road trip a region because it turns out to be cheaper than buying train tickets for for people for long distances. I highly recommend using Holiday Autos for their reliability and low prices. They compare 1,500 car hire companies to find you the best price.