em Client consumes less memory than ThunderBird

I am still trying out eM Client before I buy a copy of it.

I have been comparing it with the latest Thunderbird that has most recent cutting-edge stable  features, which Mozilla calls EarlyBird.

And I found one interesting thing and that is:  eM Client always consumes less memory than ThunderBird, which can be seen in screen shot below of Task Manager taken on my laptop. I observed this pattern over a few hours of both email programs being up and running on my laptop.