This is primarily personal preference; and keep in mind that coffee can vary in flavor just by sitting after brewing for a long time, or if you add sugar, creamer, flavorings, etc. to the coffee.
My personal opinion is to rate Starbucks , Tim Horton, and dunkin donuts as my #1, 2, and 3 picks, for best coffee of the three choices you offered.
Peets coffee is really good, and I enjoyed Kiva Han in Pittsburgh a lot. If we were in Seattle or Hawaii, all bets are off - Seattle has awesome coffee all over the place, and Kona coffee - especially fresh made while visiting Hawaii, is exceptional.
I enjoy a good cup of coffee. Disclaimer: I do own some Starbucks stock.
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