Tirano to Chur

Bernina is a nicer experience, better food and drink service, bigger windows. We love it. However I can't compare to regional trains as I have not done that. Regional is obviously cheaper, probably slower, and some people say its nice that its windows open for fresh air.

We did the regional train Sept, 2021. These trains were not crowded at all, lots of space between passengers, you are free to move to each side of the train [for pix], more scheduling options, no seat reservations needed, and the windows open for fresh air and glare-free pix! You are on this route for the views, not the seats. In fact, I never had so much exercise on a train ride, as I moved from side to side for the incredible views. Either way, it's a spectacular experience!

If memory serves, the Bernina express is direct to Chur whereas the regional train requires two transfers in quick succession (Pontresina & Samedan), or a poorly-time one in St Moritz.
This skews the balance towards the Bernina Express, in my opinion.

You are correct, there are a few changes we need to make.

Upon more research and info posted here, we have purchases 1st class saver tickets for the regional train. We aren’t big on touristy stuff and love the idea of moving at our own speed. Thanks everyone!!