> Please tell those of us in the dark what is meant by 'core-spun.'
A thread often consists of many parallel fibres all twisted together. Been that way for the last few thousand years.
When the fibres are cotton the thread is weak, and UV degrades as well. Some quilt makers love the stuff though. Cheap.
When the fibres are all polyester and very, very long (essentially infinitely long), you have a much stronger thread, but one with some disadvantages.
* The surface is very smooth, so finishing off a line of sewing takes a bit more work if you don't want the sewing to come undone.
* The thread can develop kinks if it has a full machine twist, so running it through a machine can be tricky at first. (A cheap almost untwisted version exists for use on sergers, but it is totally unsuited to ordinary sewing. Avoid it.)
* When sewing at high speed through synthetic fabric the needle can get hot. With the thread whizzing backwards and forwards through the needle, the eye can get even hotter. Now stop the sewing, and see if the thread melts slightly where it touches the needle. It can. Oops!
You can randomly blend cotton with polyester to get good dye uptake, but that is cheap stuff. Instead, start with a core of polyester fibres, and add a layer of continuous polyester filaments and cotton fibres around the outside. You end up with a strong polyester core with a cotton sheath. When this runs through the needle the cotton reduces the friction so the heating is less, AND the cotton protects the polyester core of the thread from melting when the needle gets hot. This is core-spun poly-cotton. Very widely used industrially.
I read a comment somewhere that 'Friends don't let friends use Coates'. It may be OK for amateur quilt enthusiasts.
A pretty 'average' consumer thread, made to a price.
Metler Metrosene Plus
Straight polyester thread, no cotton. Slow speed.
Sorry, I don't know them.