The "flat as possible look" as compared to the "puckered as possible look"
 

Which do you prefer - and why?

And how do you achieve the look you prefer?

I prefer "flat as possible" - because I think it lays better on a bed and/or hangs better on a wall.
I also want to have a fairly good idea of what the finished size will be after it is completed. I know that quilting (especially dense quilting) will "shrink" the item somewhat, too. There is still some "puffiness" after the item has been quilted and washed a few times.

I achieve that by shrinking/washing all the components I can before cutting them.

I am not a fan of puffy. I too prefer flat for pretty much the same reasons as you do. I like the way it hangs and looks on the bed.

I however do not do much prewashing except for flannel which I have had shrink up to 3" to 4" WOF. I compensate for my choices by using a medium density quilting pattern when I quilt. So far I have been lucky, I guess, as so far I have not had issues with fabric dyes running or uneven shrinking after washing.

What batting do you use? Do you prewash it as well?

"Comfy" looking. Not flat as a board, a little puffy but not puckered.

I prefer an unpuckered look because the prints on the fabrics and the piecing design are clearer.

I like the look of a medium finish. I like to see the effects of the quilting and love the look of designs like feathers where the space between the stitching puffs up a bit. So I don't like it puckered up too much either because I find it hard to see the actual quilting lines.

Depending on the quilt is how I decide if I want flat or puffy. The quilt I am working right now I want a bit of puffy. It is a baby's quilt and so a little puffy is desirable. Wall hanging I want very flat so pre-wash and shrink as much as possible and then quilt closely. The quilts currently on my bed are very flat. Pre-wash W&N batting quilted closely. The primary one in my guest room is a bit more puffy. It has a poly bat still quilted very closely but has a bit of 'puff' to it. Now I have a hand quilted quilt with a poly bat that has a bit more puffiness to it as it is not quilted as tightly as some of the machine quilted ones. So what I am getting at is that it is all up to what you want as the final outcome of your quilt. I think of all these things too when I am making a quilt.

I think there is a difference between "puffy/fluffy" and "shrunk unevenly/waddy" looking.

the look i want depends on the quilt design.
sometimes flat is best.
others benefit from a bit of puff.

howze that for a wish-whashy-not-a-real-answer? lol

I prefer the flat look in my quilts. I always prewash and dry my fabrics. After I complete a quilt, I launder it, dry it in the dryer and then iron both sides to restore the flat look as much as possible. I also use an 80/20 blend batting. I don't quilt my quilts heavily, because I prefer the "cuddle factor" of a more loosely quilted quilt.