I spoke with a decking expert named Chris at our local Home Depot today over lunch.
Chris had a couple of statements:
Joist hangers are stronger than nailing from the other side of the board
The joist hangers are more for anchoring the joist in a fixed position as explained here.
Gluing plywood between two sistered beams makes it a lot stronger
I researched this one a little because it made some sense to me and wouldn’t be hard to do but this article really puts it in perspective (the main point is that only some of the plies are oriented in the correct direction making a lot of it potentially wasted).
Nails have more sheer force than screws
Follow this link for an interesting debate. Apparently, as long as the design load isn’t exceeded, the withdrawl force needed to pull a screw out is greater. However, screws are more brittle so if they are “overdriven” or subjected to a lot of repeated stress (wood warping, foot traffic) they will break whereas nails will bend and bend.