Puppy is a great choice for low-specification hardware or occasional use but, if your hardware allows it, we would advise looking at one of the "big three" if you are looking for a serious long-term O/S.
Actually its not Ubuntu. So what ever advantage you know on Ubuntu wont be here.
I guess still more releases to come to make it better.
According to Wikipedia Puppy Linux is an operating system and lightweight Linux distribution that focuses on ease of use and minimal memory footprint.
The Disadvantages of Puppy Linux
Puppy has a conservative approach to new technologies
Puppy differs in many ways from of its sibling
It is based on Ubuntu, environment , it means that much of the software available for Ubuntu will also work on Puppy