Tenants in common gives you more protections and you can specify in a deed of trust what you would want to happen in the event of relationship breakdown (eg if one of you has first dibs to buy the other out, or a time limit on doing so etc) which is definitely better to decide now whilst you still like each other!
Joint tenancy is most common among married couples because it helps property owners avoid probate. Without joint tenancy, a spouse would have to wait for their partner's Last Will to go through a legal review process—which can take months or even years.
Further tenancy in common allows parties to hold unequal shares of property interest. Joint tenancy requires each co-owner to hold equal shares of property. Further, co-owners must transfer the deed at the same time. In this sense, joint tenancy is rigid compared to tenancy in common.
Joint tenancy property passes to the surviving joint tenant and no one else, no matter what you do. If it is your intent to leave your property to your spouse and then to your children, joint tenancy is not for you.
If multiple people hold title under tenancy in common, this means that each individual can choose to sell their ownership interests in the property at any time. Unlike with joint tenancy, a tenancy in common agreement allows for multiple owners to own different percentages of the entire property.