Although I have tried out many supports over the past few years I return to the same favourites:-
Arches Hot Press Watercolour paper or Mellotex for graphite
Polydraw Drafting Film for coloured pencil, or mixed media including acrylic
Ampersand Pastelbord for coloured pencil including Neocolor ll
Drafting Film, I use Polydraw double matt, 75 micron sheets. Polydraw is by West and is available as sheets or in rolls. It is described as a polyester drafting film with a high degree of dimensional stability.
I find its exceptionally smooth surface ideal for the detail I want to be able to produce. A sharp pencil point lasts for a long time on this surface. I can also easily airbrush acrylic backgrounds to produce a wonderful soft focus effect.
The one thing that you can't do on this surface is use a lot of layering, I've found 3 or 4 layers is about as many as I can manage.
If you make a mistake on Polydraw it is easy to correct, simply dampen the area and wipe off. I have even removed an airbrushed background, although that wasn't quite as easy.
I believe that an equivalent to Polydraw in the US and Canada is Mylar, and I know many artists use Mylar to great effect.
Here are a couple of examples of my work on drafting film. I have airbrushed all the background in the Rough Collie painting, in real life you can see how this pushes the subject forward.

In the Norwegian Forest Cat painting I have done the background entirely in coloured pencil, again a subtle effect but much more time consuming.

To be continued.....................