What is the difference FOR YOU between able to do this via a plugin or hardcoded in the core ?

Ahh it's simpler and not dependent on upgrading the plugin when you upgrade b2evo. And it's features i belive should be inside b2evo so that you just change a line in your skin and whoops your done.

which plugin does this ?

order by most viewed ?

Every version that existed when this thread was fresh is now obsolete. That's what happens when a really old thread gets dug up...

AFAIK there is no plugin that ever did this, although there have been hacks in the past and currently there is the mini stats plugin that shows similar info in your sidebar. I am pretty sure you can accomplish SOME of this by adding appropriate bits in your stub file ... and maybe in your index.php file - but I don't really know that or what the bits would be.

Try searching for various terms about "order by" and "stub" and stuff like that to see what's been posted on this topic. Oh and probably with ¥åßßå as the author because I think he's posted quite a bit about groovy stuff like this.