Is one or two years' postdoc experience helpful for a (nonacademic) research career?
It's hard to define "helpful": yes, it's better to do a postdoc in a top place rather than staying at home, but if you want to work in research industry, it might be better to do some development for a year rather a completely unrelated postdoc in the middle of nowhere. 

If you want to apply for a position, you have to understand the competition you might be facing: positions in the top research labs (public/private) are highly attractive, and you would be facing people with good achievements in academia (publications in top venues, PI for important grants, extensive network for collaboration, etc), and/or people with good achievement in industry (project managers, success for a specific product, good contact with academia, etc). 

So, the question is not whether it's good or not to do a postdoc, but what will a particular postdoc bring to you: 


a different research topic, increasing your multi/inter-disciplinary skills
a very promising research topic, potentially increasing your visibility by publishing at top venues
a collaboration with industry, thus increasing your academia/industry network
etc


A good approach could be to check, when available, the CVs of the people working at a research lab you could be interested to, as it could give you a good idea of what they did before joining the lab.