In addition to the incredibly helpful post above ..... :roll:
It depends on what I’m building and what its for. I have used quite a lot of mdf and biscuits but also solid wood and ‘proper’ joints. May also depend on whether the piece may need to be moved at some point in the future (e.g. a wardrobe).
Quite a lot of different options available these days.
So I ended up buying a few sheets of birch ply. It's bb grade but one side looks very nice. I am not going to stain it but paint. Reason I chose birch ply is because I am actually going to be using pocket holes ( bought a kreg jig) for the cabinets. I heard mdf doesn't take well to pocket holes.