If you are just wanting to use existing blocks Quilt Wizard is great for choosing colors and combinations of blocks. You are able to print out cutting charts and calculations for fabric needed.
If you are wanting to design blocks or do a lot of applique then you will want to use EQ7. The big difference is that EQ7 has 3 layers to work with and drawing tools. QW has one layer and less blocks to choose from with no drawing tools to alter the blocks.