If you need more storage space, it's best to choose a L. L class is typically Chevy Equinox, Ford Edge, Nissan Murano, Hyundai Santa Fe, etx - 5 passengers with more space in the back.

Q4 is a bit more of a gamble since you can literally get all kinds of stuff in that category. Nissan Rogues have only gotten smaller as they've gotten newer but you also have stuff like Ford Escape, Hyundai Tuscon, Kia Sportage, Toyota Rav4. Plus you can also get a B4 if you book a Q4 (Ford EcoSport, Buick Encore, Chevy Trax, etc) which are pretty small. If luggage space is paramount, go the safe route and book the larger vehicle. It's usually not that much more between Q4 and L.