Bob at Superior Threads has great information for threads, needle size for particular threads, tension, etc., I found this page for you:

http://www.superiorthreads.com/educa...-and-what-isnt

Now Bob is the master of threadology but personally I use all his advice except I do use cotton thread (his King Tut)...and it is a purely personal choice as I am not fond of anything polyester. I do use rayon for my embroidery work and also silk for specific things.

You can go all over his website and find all kinds of fabulous information in reference to what brand thread, needle size and so on. It just boils down to personal choice as we all have our opinions about what we prefer. So yours is not an easy one size fits all question as you can use whatever makes you happy and what you are comfortable with. Remeber it's your quilt and your way and there is nothing wrong with whatever you decide to do.

Bob has awesome short videos..from how your thread should come off the spool, to explaining threads and needles.

personally, i use what i have on hand..i just did a project, that when i was half way through..i wished i had used a shiny poly thread..it would of looked so much prettier!

the only thing i can tell you about thread,(poly or cotton) and piecing, is the thinkness of the thread will effect the seam allowance.
i use gutterman, connecting threads spools,thier cotton and poly, and bottom line thread,master piece etc... i am not fussy. just personal preference.

It's a matter of personal choice.

I say, 50wt cotton for piecing and whatever floats your boat for quilting :)

Yep personal preference. I prefer poly for things that will get a harder life. Such as kids clothes. Poly is simply stronger.
Cotton is softer but will also fray faster.
They both have their pros and cons. I have a mixed drawer of both.

I to am confused But, my dealer at Viking said that Quilts made with Poly will come apart in time, the poly will 'cut' the fabric as the cotton ages so they don't last as long as a all cotton Quilts and its best to use cotton so you leave a Legacy! 8-)

Poly will melt with a hot iron, so if used you need to be careful of that. I stick to cotton for piecing and usually use cotton for quilting. Unless it's an art type quilt and then anything goes.

I don't think it matters which thread you use. I've been quilting for over 30 years using both; all the quilts have been washed many times and they're fine.

I'm a Bottom Line devotee
http://www.superiorthreads.com

I use Aurifil 50 as top thread when I need to use cotton; e.g., my Jems won't take BL on top if it's in the bobbin.

I use both, but mostly cotton for regular piecing. Poly has come a long ways, and it is nice to use. Though I do not use Gutterman-don't like it. Superior's threads are fabulous! I also use Connecting Threads stuff, Signature, and Aurifil is my favorite! :)
Just use what you like, and what works well in your machine. :)

I usually use thin poly thread in my bobbin and cotton for the top thread. I use both in any combination or alone.