For Canadian travellers, one detail settles Kindle vs Kobo: free library e-books. A Kobo lets you borrow them from your public library right on the device. A Kindle can't do that in Canada; the feature is US-only.
That's the whole argument for most people. Link your library card once and you can borrow a stack of books before a trip without spending anything. Kobo is also a Toronto-based company, and its e-readers read EPUB, the format most library and non-Amazon books come in.
Which Kobo
The Kobo Clara BW is the one we'd pack: a 6-inch glare-free screen, waterproof (fine at the pool or beach), and small enough for a jacket pocket on the plane. If you want a bigger screen, the Kobo Libra Colour has a 7-inch colour screen and physical page-turn buttons, which are much easier one-handed in a cramped seat. Colour is nice for maps, comics and covers too.
When a Kindle still makes sense
If you already own a big Kindle library, or buy most of your books from Amazon, the Kindle Paperwhite is still excellent: waterproof, weeks of battery, and a great screen in the sun. Just know you'll be buying books or using Kindle Unlimited rather than borrowing from the library.
Protect the screen
E-reader screens crack under heavy bags in the overhead bin. A sleep/wake cover made for your exact model protects it and saves battery by waking the device when you open it. Sizes change between generations, so match the model.
Before you go
Download library loans on home Wi-Fi; holds on popular titles can take weeks. Once a book is on your Kobo, it reads offline until the loan ends. And since one charge lasts weeks, you can leave the cable at home on short trips.