I've done both, boarding and kept my horses at home. In terms of cost, there are many factors to consider. Keeping horses at home, you don't have the outright cost of board, but there are many hidden costs and it isn't cheap when you add it up.
First off, you have the cost of the property itself. Rural property is an investment, however the rate of return when you sell depends on economic conditional. If the economy dives, people want homes in town, closer to their jobs as rural property is seen as a luxury. Property taxes can be high and upkeep can be costly. Replacing or fixing big ticket items such as septic fields and drilling wells can add up quick. You need to be able to afford to do repair these things if they break. With horse property in places that freeze, water lines are also an issue. You will also have the cost of fencing, upkeep, power, water, pasture management and extra insurance. You will also need the equipment to do the work on an acreage, which is expensive to purchase and maintain. You will also have to buy feed in the winter and depending on the year, you could pay dearly for it. Around here, hay producers honour their contracts with the bigger facilities first before they sell to individual acreage owners. When boarding, these are all factored into your board. Most properties don't have a designated place to ride, while many boarding facilities do. Also, unless you have a trailer, you may pay extra to bring out the vet one farrier. At a stable, this cost is often shared because the vet or farrier will do multiple horses in one visit. When you keep your horses at home, you need to arrange care for them when you go away. This is the wot difficult part of having horses at home for me. We don't go often, but it is very hard to find someone reliable when we do.
The work can be intense or minimal depending on your set up and your expectations. I spend on average about an hour per day looking after my four horses at home. They are pastured and I am fairly fussy about things, so I think that an hour a day isn't bad at all. That doesn't include upkeep on the property and maintaining the fences and my horses are almost always on pasture even though we have a barn. I had one horse who was on stall rest for about 2 months and my time requirement doubled. In summer, if I don't have to blanket for flies daily, I get away with about 10 min twice a day checking horses, checking fences and checking water.
All that said, despite the work, the cost and the commitment, I love having my horses at home. I don't think anyone on the planet cares for them as well as I do, and it is a labour of love. This is why I choose to do it, not because it is any less expensive. Having lived in town and boarded two horses, I found I had far more time to ride, and it was actually cheaper (for pasture board).