Working on butt wink . Great explanation of importance of hamstring flexibility link to very good Article called Hamstrung by Kelly Starrett in July 07 Crossfit Journal discussing how to measure and improve hamstring flexibility .
There are 2 variations of the deadlift that are best used for strength gains; the conventional deadlift and the sumo deadlift. The romanian or stiff leg deadlift is more of a supplementary exercise. The conventional deadlift is the best option