I just helped a friend set up his new (to him) Kobo HD and I'm pretty impressed with that thing. It seems very solid and has a very good screen. It's bigger than I like but it's really an impressive device.
I have a Paperwhite 3 and think it's excellent. Very sturdy. The Kobo HD seems sturdy as well. I have the original Kobo Aura, bought new shortly after they came out, and looking at it now after years of use you can't tell it from a new one. It's certainly sturdy. It's also been in my pants pocket a lot so it's probably had rougher treatment than most of my devices. It hasn't hurt it a bit.
Last, and certainly least, I have a Nook Glowlight plus. It does seem sturdy. It's the only reader I have without a case, mostly because I don't like it enough to invest in a case for it. I use it for loaning books to neighbors mostly and it's held up well. I bought it new the day they were announced.
The Glowlight Plus has 2 problems that keep me from liking it or recommending it. First, it's home button is capacitive so if I touch the front near the bottom it takes me back to the home screen. That's exactly in the most natural spot to hold it. This is easily the stupidest (I don't like that word but it's so apt here) design decision in the history of technology. Imagine designing a car with the brake pedal hidden under the accelerator. That would be comparable.
The other problem with the Glowlight Plus is that when you long press a word to get it's definition, that definition is in grayed out text that's nearly impossible to read. This is so dumb that it can best be described as viscious design. A user sadistic interface!
Other than those two killer problems it's actually a really nice device. It might have been my favorite ereader but it's just not something I like to use, as is. I have tried half covering the capacitive button with an adhesive backed piece of felt but I need access to that button and the only way to avoid having it send me to the home screen while reading is to make it totally unavailable.
I strongly suggest not getting the Nook. And that's sad because it's such a near miss. Everything else about it is great.
As for the rest, pick one and that's the one for you. They're all great choices. Toss a coin if that'll help. You can't go wrong.
Barry