For me, there's no difference, just that "puis" is more informal i guess than "ensuite". Moreover, its better to use "ensuite" at the beginning of a sentence, it doesnt sound good at the middle. With "puis" it doesnt matter.

both are the same 

The two words are interchangeable. The exception is that "puis" can only be used at the beginning of a sentence where as "ensuite" can be used everywhere in the sentence.