Medium seems to be the sweet spot for plenty of page space in a portable size book. Here are the Quo Vadis planners that come in Medium size. You can click on the links for more information about each planner, including purchasing information.
These planners are all 6 1/4 by 9 3/8 inches, and are slim so you can carry them easily in your bag.
The academic year Scholar weekly planner has an open format for scheduling and notes, and has monthly planning pages:
The Academic Minister planner allows you to plan your schedule to the half hour:
The Minister planner has the same format, in January-December. Bonus: the 2017 Minister planner now has monthly pages!
The Space 24 planner has the week’s schedule on the left and the right page lined for lists and notes, and monthly planning pages:
The large Rhodia planner has a similar format, with the right page gridded for lists, sketches, charts and graphs. The 2017 large Rhodia planners have monthly pages too!
The Hebdo weekly planner has the same format as the Scholar, open for scheduling and notes. It also has monthly planning pages:
All of these planners measure 6 1/4 by 9 3/8 inches and come with a variety of cover options.