Free Peek Before Calling the Bigger Box

Two boxes each independently contain an amount drawn uniformly from $\{1,2,3,4\}$. You must guess which box holds the strictly larger amount; a correct guess pays $1$ and a tie or wrong guess pays $0$. Before guessing you may take a free peek at the contents of one box (your choice of which). By how much does this peek increase your probability of a correct guess compared with guessing blind?