Hi,

Which is preferred? What are benefits / drawbacks of each?

Thanks

Hi. This depends totally on your needs. Of course DISQUS is by far most advanced than the build in K2 comments.

can you please outline broad 2-3 differences?

I need a simple system for replying to the articles. A threaded reply system would be preferred.

K2 comments does not support replies, so in your case you might need DISQUS. In any case, DISQUS is a free service, you can evaluate both systems and choose what you think is better.