When three inventors file a provisional patent application, should we file under our individual names sharing the patent or under our company name?
Either option is ok, from a legal point of view.
However, joint ownership can be quite difficult in practice. Generally any changes (such as assignments or licensing) require the assent of all the joint owners. If there is any kind of disagreement or falling out between the co-owners, the patent can become quite hard to administer.
By having the patent held by a company, this is somewhat simpler — the company would administer the patent in the same way that the company makes any other decisions. Of course, it would be a good idea to determine who makes the decisions for the company in advance, otherwise you may well end up in the same position as if it were joint owners.