There's a huge rumor on the Internet that tomatoes taste better unrefrigerated, and pretty much everyone who says anything about it on the Internet believes it.
I've tried both, of course, and here's my opinion:
Tomatoes don't taste better or worse when refrigerated. They taste different. When refrigerated, they tend to be firmer, and have a nicer taste/texture for dicing and such, in my opinion. For eating fresh, I'd suggest keeping most unrefrigerated (and eating them sooner than later). For tomatoes you'll be storing for a while, I think they tend to taste better refrigerated (unless maybe you're going to cook them afterward or something). Unrefrigerated tomatoes continue to ripen faster (and get softer faster, which is fine for juice, but not the best for dicing and literally slicing).
Refrigeration may reduce certain flavors.
One variety I think tastes better refrigerated is called Valencia (a medium-ish orange tomato).
Tatiana's says that it is claimed that Black Pearl F1 (developed by Burpee), when refrigerated, develops "a unique extra sweet, 'Concord' grape flavor". She seemed skeptical to me, though. I'm not terribly skeptical, personally, but I understand why someone would be skeptical.
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USDA hardiness zone: 6
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