Having used both, personally I highly preferred the Pebble over the Bangle JS.
Pebble was solid software, good designs and it all just worked simply and did what I needed. I also thought the Pebble Time Round was near perfect in design and execution. I'm not a fan of the geeky look of the normal pebble and bangle watches (or the apple watch look).
The Bangle was fun to dev for, and I love that it exists, but it all felt like a dev project. Not a finished product. Granted it was early on in the project so I'm sure it's in a better place now.
They both have similar capabilities. I say go with whichever you think is going to fit what you need a smartwatch to do.
I made the switch to Kagi January last year.
I know it's all just personal experience and everyone can have their own needs, but I was skeptical at first as well.
Almost a year and a half later I've got no complaints.
My searches feel like how Google felt years ago: mainly I never think about it. I search, find what I want and I'm off. It just works as I'd expect without the nonsense ads and AI Google has now.
Worth a free trial. See how it works for you.