IIR this subject created a pretty long thread a few years back. Bottom line is, whatever works for you. This is similar to the dovetail pins/tails first discussion that pops up sometimes. Both approaches have pros and cons. I build boxes first and then face frames and then scribe ff's where they meet walls, etc. I don't use grooves to align ff's and cabs, just dig out my trusty biscuit joiner for alignment. Fast and easy and have never had a failure at the ply/ff interface. If one wants to spend time cutting dados and rabbets my hats off to them.