Shush/pat and pu/pd have slightly different goals. Shush/pat is meant to help soothe your baby to sleep before your baby has the skills to do so herself, but to help soother her in a way that sets you up for independent sleep in the long run by getting her used to falling asleep in the crib. Pu/pd is meant to teach independent sleep to a baby who is old enough to have the ability to self-soothe (which usually, but not always happens around 4 months). So, I wouldn't say one is more successful than the other because their objectives are slightly different.
I'm a fan of pu/pd and in a way, for certain personality types, pu/pd is easier because your direct goal is teach fully independent sleep, so you are constantly working at removing yourself from the falling asleep process and getting baby to do it his/herself. With shush/pat you are offering some soothing (but in the crib environment) because baby isn't quite old enough/mature enough to be able to fully self-soothe.
If your LO is old enough to have the resources to fall asleep independently, it may take you a week or two of REALLY hard work and lots of crying (with you right there) with pu/pd, but in that process they figure out how to self-soothe and then, for the most part, you can wind them down, pop in the crib, and walk out and they'll go off to sleep on their own.
Remember though that pu/pd is meant to be a last resort when other methods have not succeeded. Depending on your LO's personality, shush/pat is the preferred first method because for a baby who responds well to it, it's a gentle way to help that can be gradually phased out to get you to the same end goal that pu/pd does--putting baby down and baby falling asleep without assistance.
