Such a joint marital trust will commonly provide that the property of the first spouse to die will go to his beneficiaries upon his death. Since most of his property will likely go to the surviving spouse, it winds up back in the living trust anyway, combined with her property. Remember that such a set-up transfers the property to the other spouse with no conditions of any kind. Also remember that in most states, divorce does not automatically invalidate a living trust. If you want to maintain more control over your property after you die, talk to your lawyer.
Most living trusts are revocable.
It can also offer a bit more protection from creditors. If you make the trust irrevocable to reduce taxes and avoid creditors, prepare for a lot of paperwork. And understand that you lose the flexibility of a revocable living trust. Be sure to consult a lawyer before setting up an irrevocable trust. Everything you need for court related issues.