I also use washable markers, but be sure to test on scraps first! I use poly all the time and have no problems with it bunching....you just have to make sure your quilting is within the guidelines on the packaging (the quilting lines for most poly is 3-6"). That is the quilting lines (or ties) should not be more than 3-6" apart in any direction. Poly batting is warmer, but also comes in different thicknesses (loft) for different uses. There are many different battings to choose from and each one will have its advantages.