If you're married, it's important for both of you to have enough life insurance to cover in the event either of you dies. This can get very expensive, but one way to do it for a little less is to buy a survivorship policy. This kind of policy is similar to a joint policy because the premium is determined by the average age of both of you.
Also like joint life insurance, it's a bit cheaper than buying two separate policies. The biggest difference between a joint policy and a survivorship policy is that the joint one pays out only on the death of the first spouse, while the survivorship only pays out on the death of the second spouse.
Basically, a joint policy is focused on covering the surviving spouse, while a survivorship policy ensures you leave a death benefit behind for your other beneficiaries, possibly your children.
If you do start considering a survivorship policy, just make sure you've got enough other coverage for the remaining spouse after the first spouse dies.
However, you may want to consider a survivorship policy if you've got a large estate you'll be leaving for your children. This kind of policy is perfect to leave your children enough money to pay the estate taxes your children will owe after your death. When selecting a policy, choose one that will leave enough money to pay your final expenses and your children's inheritance tax. Also don't forget the death tax, which will be owed on all the assets and cash you leave behind.
Choosing life insurance can be a tedious task, but just take your time and compare coverage and premiums from several different companies. Survivorship policies aren't for everyone, but if you do your math carefully and determine exactly how much money your family will owe upon your death, the policy can really help.