People new to the craft of weaving are usually looking for definitive answers to what they think are very simple questions. They are expecting a simple answer to their simple question.
The problem is, weaving (like life, really) is anything but simple. In fact, it can be quite...messy...in terms of the things that need to be factored into any decision.
Since the vast majority of people learning to weave are doing so as a pass time, a hobby, perhaps a long held dream to make their own fabric, or even just an undefined desire, many expect to be told to do x, y and z and then they 'know it all'.
But it isn't that simple. There are very few 'black and white' considerations when it comes to the creation of a textile; rather, there are many different shades of grey.
Although I've posted about this many times before, I will use this example again of how things...depend.
In the photo above there are two skeins of cotton. Both skeins are the same in terms of how many yards per pound have been spun. Can you see the difference between them? (Biggify the photo for a closer view.)
Even though they are both 100% cotton at about the same thickness (or grist, or yards per pound), they are quite different and they will behave differently.
First of all there is the staple length. One has a staple length of approximately 3/4" which is about the shortest staple length used to spin yarn. The other has an average staple length of just under an inch.
One was carded (the shorter length staple) and spun open end which produces something akin to a woolen spun yarn - lofty, more air in it, weaker than the other - which was combed, ring spun, more like a worsted yarn.
So yes, even though they both have the same number of yards per pound (approximately) they are two very different yarns. They will behave differently as they are used and will make cloth with different characteristics.
Which is better? (Wait for it.) It depends. What type or quality of cloth do you want to make? The shorter staple loftier yarn will be more absorbent, but weaker. The other yarn, more tightly spun, will be stronger, but less absorbent.
See? No simple answers!
And so it goes for the entirety of the craft. (I am quite sure other traditional hand crafts have similar complexities, but I'm most familiar with weaving.)
So, new weavers, ask your questions. But don't expect a simple answer because the correct answer in almost every case is...it depends...