What's the difference between a monthly-only and a weekly + monthly planner?

A monthly-only planner gives you a single two-page spread per month for big-picture scheduling, which keeps the book thin and cheap. A weekly + monthly combo adds dated weekly spreads behind each month, so you can break down day-to-day tasks. Several picks here (the Blue Sky and bloom academic planners) include both layouts, while the budget AT-A-GLANCE and POPRUN options are monthly-focused.