I have both. If it were just me and my wife, we'd do cell phones only. But having kids, a land line phone is the cheapest solution on a phone only consideration. But we also use a very cheap pay as you go cell service as the phone isn't a big part of our lives.
But you also need to consider bundling issues. TV, wireless, and phone are often discounted and sold in bundles that complicate the decision. My internet is DSL and that affects my land line and bundled pricing. Or you might be part of a HOA that contracts certain services at other discounts. Lots of variables.
Also consider what service has the best coverage for where you live and where go. There are a ton of dead zones in my state and my particular neighborhood has crappy cell service (and over the air TV reception).
Land-lines with a cord are the most reliable phone. They work in power outages when cordless phones won't. Cell phones might work depending if you're in range of a tower that has power.
In a big disaster, the cell phone probably has more usefulness, as it's likely to be restored sooner (assuming you have a way to keep it charged) or be useful if you're out of the disaster area.
Phil