I have used coats with not problems. If there are alot of small stiched in a very small area I due get breakage.
I have used Spectra, and it is not an easy thread to use. I use a wide eyed needle and set the machine at the slowest possible speed. I don't use a vertical stand next to the machine or a multiple cone rack, as the thread then twists as it comes off the cone. Even the packing peanut method does not work for me with this type of thread. Instead I put the cone on a vertical peg of the machine, felt beneath it so that the cone can turn and unwind, that prevents twisting and kinking.