I haven't done the experiment yet, but I will. I mis-wrote my 50% - I was thinking 50% more of "up and down" thread - the horizontal distance would be the same.
Yeah, the biggest change would come with thick fabric or layers, which is not really an issue with piecing, but would be with quilting. What got me thinking about this was the HUGE stitches you see on mass-produced quilts and comforters. You know the manufacturers of things like that are aware of even the tiniest extra cost...so there must be some penalty to making small stitches on low-cost items...
Alison