I am not an expert but I am in the process of making my first cuben tarp. I have some sewing experience ,I made a suit of sails for a DIY dinghy in my youth, but I am not as comfortable with a sewing machine as Tim clearly is. I am quite good at glueing things. My first conclusion is that either method will work.
Hysol is good glue and its peel abilities may not need to be improved by sewing. If you are having a straight ridge seam it would be reasonably easy to lay the pieces out flat and glue them together. The stronger the cuben you use the more likely that sewing may improve the peel strength of the hysol. If you use a cheaper glue like Aquaseal you probably need to sew to improve the peel strength.
If you are cutting a catenary ridge, glueing something non flat I can see being a problem. My choice, I am using the 0.74 cuben and using a catenary seam is going to be put the outer faces together sew with maximum stitch length with 1 minimum seam allowance and one generous glue width allowance 3/4"?. Open the materials up, flap down the glue seam hiding and creasing the minimum allowance in the process and glue down and press the seam. (Hysol does not stick to polythene, so separate things that should not stick together with a plastic bag) When it is set I may run another line of stitching down the other side of the glued seam. Done this way I think the sewing is done while things are flat and then the sewing helps position things to get the glue to set to the right curve.
Sewing is quicker, cheaper and less messy than glueing. I believe that ultimate strength is obtained by including glue but ultimate strength is not obtained by doing it wrong and getting an uneven seam, where the tight bit takes all the strain! I think the .74 cuben is so strong that ultimate strength may not be the most important crieria