I will be in Guatemala with my family in a couple of weeks. There's 5 of us, and I am still trying to weigh up whether I should rent a car or rely on public transport.
I'm not looking to get a debate going on the non-cost pros and cons, like convenience, safety, etc. I am experienced with renting cars in Latin America and know the deal.
We will be doing a two week itinerary, whereby we take in Antigua, Atitlan, Chichi, Coban, Tikal, and back to Antigua.
It looks to me that car rental is cheaper (for me). Yes, public transport would be cheaper if we rode on chicken buses, but they are not really practical for families traveling with luggage. Public transport would therefore be the private minibuses that work the roads between towns and villages. I've used them before, and although reasonable, can be quite an item if there's 5 of you and use them a lot.
I got an online car rental quote from Tabarini and it seems quite reasonable. Their quote included the car rental, insurance, and sales tax. Unlimited mileage. I am assuming that the total price they quoted is the actual final price, as I've had the occasional issue in the past where the quoted price doubles when they draw up the final bill. I have an email into them asking for clarification.