Thread is thread is thread. Asking about the best thread is like asking about the best machine. You will be confused about all the different answers. Someone soon will be along to confuse you further about what weight of thread to use.
For the last two questioners:
1. I have mixed threads on quilts many times ( cotton and poly and cotton-poly)and nothing happened. For piecing I use up all the odds and ends I have laying around or good old Coats and Clark..
2. For quilting I find the best color match and shine level I want regardless of brand. (Or cotton or poly or ctton-poly.)
None of my machines - two Pfaffs, a Viking, a Kenmore, and a Featherweight - care a wit about what thread is going through them.