The word "joint" when discussing a form of co-ownership almost always refers to the arrangement whereby a deceased co-owner's interest passes entirely to the surviving co-owner. The transfer of the decedent's interest happens automatically, without the need for a probate proceeding. The only documentation normally required is a certified copy of the death certificate and a sworn statement which gives some basic facts about the decedent, the decedent's death, and some identifying information about the survivor. In a nutshell, the answer to the question is "Yes" as to avoiding probate.
The answer to this really depends on what your overall goals are for your estate plan, and what the tax liabilities of your estate might be. If the property is in joint names, either party can access the funds at any time. If it is held in one name alone, only that party can access the funds. The beneficiary can only obtain access to the funds when the primary account holder has died.
