Designer: Josef Muller-Brockmann
This poster is a modernist poster. This is clear as the type is all left alligned and a modern typeface is used (Helvetica). It's also apparent that it's modernist because a grid system is used and stuck to closely. It also has a great focus on negative space and it's very legible.
Designer: David Carson
This poster is a post-modernist design. We know this because the type doesn't follow a grid system and there isn't a great focus on legibility. It's also apparent as the type is overlayed ontop of each other to create layers, and there isn't a grid system.