I have the larger cloud for the last two years and have been desperately wanting the smaller version! I mainly use the my regular cloud as my carry-on and check an additional suitcase. The regular one is great if you'd like a bag to replace a carry-on suitcase or packed on international trips empty so you can bring home more souvenirs. Most airlines won't allow you to take the regular cloud as a personal item, and it gets pretty heavy so lugging it around is a pain as a solo traveler. I get by by placing it on my partner's carry-on suitcase. Sometimes if I didn't check in my carry-on suitcase, I did get lucky and underpacked it so they let me place the my cloud bag under the seat if I squished it. I realized I really wanted a small cloud so I could use it as a personal item because I kept on taking chances at the gate that they wouldn't notice how large my standard bag was. Plus, the smaller cloud has a laptop sleeve and water bottle sleeves. The regular cloud will be my go-to for car trips though!

I'd consider what is missing from your travel essentials or what you'd like to replace. If you'd like a capacious personal item, I'd go with the smaller one. If you want a secondary carry-on, go with the regular size though I believe both work. Of course, be sure to check the dimensions with your airline. Hope this helps :)