which one is better for SEO bold or strong tag

Before a few days ago i gone for a meeting, the meeting is in between a company and thier client, the company was doing their website designing development and SEO work.

The company used strong tags on all over the website where required to highlight the keyterms and when i started discussion with the SEO and development person about the H1 tag and other tags then they understand i was pointing out strong tags.

They really surprised and asked me what is the difference in these both tags, as their functions are same for the user, I understand that they are really not familiar witht the Google visit index and cache hence they are saying these words, but they are ready to understand my logic.

And really I was not in mood to explain them theory of search engine , Google and SEO, so I open two pages of different sites where one site used bold tag while other one used strong tags, for user both sites are same, but when i check indexed version of both sites content under bold tag was bold visible to Google too while strong is shown very normal text to Google.

That's the points that I was actually wanted to explain them, and I think this practical approach make them more understandble them  then a theory class.

My task was completed there.

Specialist in SEO Services Delhi, India