The most important benefit is cost. If you're on a tight budget, they will give you the most bang for your buck. If you're buying one of these for your son or daughter to see if they will enjoy playing and stick with it, it's a great way to test the waters.
I searched for best prices, quality and buyer reviews when I was choosing the five products that made the cut. I actually bought my son the Ibanez kit many years ago and he's still got it. He's graduated to a bigger and better setup, but it was perfect when he was starting out.
Electric Bass Full Size Beginner Pack
PJ Electric Bass Guitar with Rumble 15 Amplifier
Jumpstart Bass Guitar Starter Beginner Pack
Edge Electric Bass Guitar with Amp Case Strap
Bass Guitar Starter Beginner Pack