It depends on the design of the quilt. 9 patches for eg are generally done in rows which then get sewn together.
But a design which is created over say 4 blocks making a big square 4 times wouud be sewn together into the big squaris and then the four big squares (each made up of four square blocks, which are in turn pieced) sewn together. Think along the lines of a compass/exploding star quilt design.
Any quilt which can be chopped into quarters in order to get tight points and maximum lining up should be sewn into the quarters and then quarters together (obviously some have another row of same sized blocks so you have 6 big blocks instead of 4 etc).
Bargello quilts are always done in strips and they are then sewn together from the middle out, using sew up, sew down technique to avoid a bend.
Inconsistent blocks are always sewn into larger consistent block shapes which are then sewn together. Inconsistent blocks are when you have a few blocks of different sizes (like in Imi's BOM) and are frequently found in sampler quilts. You sew them into bigger squares or rectangles so that you can sew the big blocks together more easily.
And personally, if I am making square blocks with a lot of pieces on the bias I tend to sew them together into bigger squares/rectangles to stabilise them a bit, otherwise you can get stretched fabric or bendy seams if you do long rows of them.