I love guys like Lang, who are defensive studs at C and not a total zero with the bat. That said, Payton is way better.
If I couldn't trade Lang for equal value, I would start Payton against RHP and Lang against LHP for the first 130-140 games of the season, because Payton can't start more than about 110-115 games without fatiguing. Then, down the stretch and in the playoffs, Payton becomes the full-time starter. Use Lang as Payton's defensive replacement at all times.