When making multiple unites of the same thing, I make one "practice" one first, since I can learn a lot from making that first quilt block or tote.
After that I usually lean towards mass production over one unit at a time. There's some limit, though. If I were making 100 totes, I wouldn't do each step for all 100 before moving on to the next step.
Sometimes I'll do all the cutting for a quilt at the beginning before sewing anything except the practice block, but sometimes it's more than I can stand to do and I move on before the cutting is done. The downside of not doing all the cutting for a quilt at the beginning is that I'll lose track of how much more I need to cut of each fabric. Then I'll end up with 46 blocks when I need 48 and have to pull out the fabrics and the cutter again. For some reason I really hate that, probably because I thought I was done when I wasn't!