the bottom joint would be the best joint, and can be cut with a table saw, im not to sure a circular saw would workthis is a biscuit joint (id make the 'biscuit' larger tho)
or you can do a tongue and groove (just get the router bits)
here is a bridle joint - pretty similar, but bigger tongue and groove. not sure how well it would work with MDF tho.
thats a rabbet joint heres a dado