stiff are great, if your having pain in one side and not the other as mentioned bro, it may be a slight alignment problem in your posture and i would suggest trying the stiffs with dumbells in that case and then see how it feels compared to barbell straights, i also believe stiffs are a staple exercise not to be over looked in your training, but as dorian said and i only agree with the risk issue becuase ur already experiencing pain, then i would say stick with the other movements that dont hurt if their isnt any pain in those movements, but in a healthy person i dont (personaly) think the risk out wieghs the benefit in a generraly healthy person when it comes to stiffs