On a warranty deed that reads Joint Tenants with right of survivorship, what is the difference with Tenants in common?

With right of survivorship if one party dies... the other inherits their part of the proprety. With tenants in common you don't and their heirs would get it via will or probate... meaning they could force a partition sale against your wishes.

As noted, if one joint tenant dies, their share goes to the other joint tenant outside of the estate. With In common, their share goes to their estate.