I also buy the sheets of the gridded plastic and have graph paper always on hand (which can be very nicely taped over the cardboard). There are certainly times when you want clear, but I make various little disposable tools throughout my projects where card board is very desirable -- like when you are near an iron! The other thing is the thickness of the cardboard is very nice, you rarely cut into it and with the plastic I'm having to line up a ruler next to the template to actually cut against.
When I first started quilting, I was about being very precise in my cutting and piecing, in the last 10 years or so I've switched to sewing/cutting large and trimming down for accuracy. Whenever possible I am using strip piecing/cutting methods and then subcutting the strips, as opposed to making hundreds of separate triangles for example. Then when you consider some of my construction methods are due to vision concerns, I've gone from basically never using templates to using multiple ones per project.
Sometimes I make what I call a "snub" out of cardboard, that is a template where I'm cutting something away. So going back to hundreds of triangles, I'll snub off the ends so that triangle will meet well with the piece it goes to, sometimes that is more square, sometimes more slanted. Snub it off so you don't get confused and get accurate results.
In addition to cardboard and plastic, we also have our rulers! I'm often marking lines on my rulers using the 1/4" quilters tape. It helps my vision issues if I don't have to count over to 2.75 or whatever -- I have a little piece of tape to guide me! Recently I had an odd measurement, something like 3.5 -- I used my tape and then I marked which direction the 6.5" ruler was supposed to go.