dodge vs. plymouth???

Plymouths were usually slightly smaller (shorter wheelbase) and had less standard trim options. Aside from cars like the GTX or Sport Fury GT Plymouth was intended to be the 'entry-level' marque for Chrysler to competed with Chevrolet and Ford. Dodge was a step above Plymouth and was meant to compete with Mercury and Pontiac. Then you obviously had Chrysler brand, and Imperial at the top (GOD I would love to have one of those...).

I personally prefer Plymouth though because 1) they aren't around anymore and 2) it was Plymouth product planners who invented the ideas for cars like the '64 Barracuda, '68 Road Runner, and '70 Duster, and Dodge merely copied those ideas.