I do what works for me after years of trying all the options and what works for me is NOT what works for other quilters. You should do what works for you and not bother with anyone else's rules.
Make some identical blocks (include HSTs or other bias edges in them), trimming to make sure they're all the same size. Press some both dry and steam, then iron some both dry and steam. Measure them all again. Note any changes. That'll give you a starting spot for accuracy.
If you're obsessive about it, you can refine that testing procedure for the best (i.e., most accurate) method for pressing seams, too. Make one block using only dry pressing. Make another using only steam ironing. Then the other two ways, then some combinations. It sounds tedious, and it is, but you'll know for sure what works best for you when you're done....and phooey on everyone else.
