Tim Hortons and Dunkin Donuts are totally equal to my tastes. Both coffee and donuts.
Which to me means they are just fine... Nothing amazing, I would prefer Starbucks, but better than nothing.
I prefer Peet's or Blue Bottle, but I guess that's just me.
I can deal with all sorts of styles of coffee. But when you're talking Tim Hortons vs Dunkin Donuts, I find they're the same price, which means Tim Hortons is cheaper since I'm paying in Canadian dollars. I've never been to a Tim Hortons outside of Canada. I've seen some listings for "Tim Hortons" in the San Francisco Bay Area, but they're basically snack bars at ice rinks that are associated with the San Jose Sharks. Apparently all they have is coffee, and it may just be brewed with whatever generic equipment they have on hand.
Well yeah I'm not going to walk past a Blue Bottle to get to a Starbucks that's for sure. Unless I was broke.. that blue bottle ain't cheap!
What sets Starbucks apart from the Dunkin, McDonalds, Hortons, etc... is that it is an actual coffee shop. If you go to a Starbucks with Reserves, you should absolutely be able to find a good tasting coffee. You may need to order a pour over, or a french press, or get it brewed on the Clover but it's possible.
The Tim Hortons in Dearborn MI (conveniently located in the Amtrak Parking lot!) is a full service Hortons just like the ones I've been to in Canada so they do exist.