Seats with inbuilt suspension vs suspension seat posts

Hi, I'm having issues with my saddle,when I go over bumps, the back side of the saddle begins to turn towards the tyre. This makes riding uncomfortable in the long run. I thought of buying a full suspension MTB but its just too costly. Found something called as suspension seat post.

But my bike shop only has those seats with embedded suspension in the seats. The question is which will solve my problem and improve riding comfort?