Highest Value - Carport or Extra Bathroom?

[Rodney Turner]

I own a 3/1 brick ranch (built in 1955) with a carport and parking pad on a crawl space, about 950 sq ft. The neighborhood is rapidly appreciating and the opposite side of the street has larger ranch homes built in the '60s, most are 3/2 with basements. Some are fully remodeled, and are selling for almost $300K. 

I am ready to refinance this house to recapture my investment, but I want to make a major improvement to maximize the value. Would that be an extra bathroom (would require adding an addition to the rear of the house) or enclosing the carport to create more usable living space? A carport would add about 130-150 sq ft to the home.