I've not used the Valdani brand, but I've used Aurifil 12wt for quilting and didn't like it. Actually ... I loved it but ...
It's very hard to match the 12wt on the top with a smaller wt in the bobbin and still maintain tension. I did not like the look that 12wt in the bobbin gave me. Using 28wt in the bobbin was better, but still too heavy on the back side for my taste.