it depends, it is said that an SR ticket also has a higher chance to pull an UR and LR due to R and HR not being factored in. we just don't know how much high the rate is.
if you're aiming for just an SR, i would go for SR ticket. just pull what you are aiming for.
or if you're like me, i want the 3x HR and 4X premium to get multiple shots. meaning it might be more likely to pull UR / LR.
so if your goal is SR units, get SR tickets. if your goal is UR/LR, get a batch of tickets. that's how i see it at least.