For me, medium curl grip BB rows. Bring the bar into the gut each rep, try holding there for a few seconds. Also have done this curl grip when doing DB one arm rows.
When doing the half row, half Hi-pulls BB movement (just cheating rows for want of a better name...most guy's can use a lot more weight in these), I use a overhand medium grip. Good power and thickness builder for me, anyway. Good Luck.