Quote Originally Posted by Apatheist View Post
You can tweak the classic client a lot to improve performance. Check out this thread.

Reducing things like particle density and view distance below the minimum available via the client has a huge impact.

I know Activision says they're going to tinker with the API but they've said they will not be updating graphics. During Activisioncon they stated they would be recreating the classic models and textures as faithfully as possible so I imagine trying out the available private server client will give you a fairly sound comparison.
Without a doubt, Classic will be using the updated game client, and most of those commands in that post have been drastically altered, are currently locked down, or are long gone from the current game client CVars, and it's unlikely that Blizzard will be unnecessarily restoring old CVars just to please the #NoChanges crowd.

The Classic game client will also be rendering in DX11, not DX9, so there's both improvements, as well as additional resource requirements, to running 11 over 9.

Finally, using an updated game client will allow Classic to run smoother. An obvious statement, yes, but, for example, the original Vanilla game client updated a player's position 64 times per second, and this created an unavoidable stutter unless you were able to properly cap your your framerate at that number, which required that your display's refresh rate was, at least, 64Hz. Perhaps there was a small percentage of people playing on CRTs that had a higher-than-60Hz refresh rate, but it was still annoying to deal with, none-the-less.