To me it depends on where you live and what your gardening problems are. In Hawaii and Florida, as soon as they turned the least bid red, bulbuls and other birds would eat them faster than they'd ripen. I did find a solution (went to a fabric store and bought green nylon net and covered them ... they'd get enough sun to ripen, and kept the birds away). I'd prefer to let them ripen on the vine until they are plump and red. Practically, though, when they are lying on the ground (we've had a wet, stormy summer here in NW IL) they will rot before ripening, so I'll pick them earlier. Also when there are a lot on one stem and they're crowding each other, I'll pick the first ones to turn orange-y and let them ripen inside. I guess, to me, you can buy tomatoes that were picked green and ripened inside all winter long, so I try to let them ripen outside for as long as possible. We have a short season here, though, and when frost threatens, everything gets picked and those that stand a chance of ripening inside, do so, the rest I (not being a huge fan of fried green tomatoes), I make into my own version of green salsa.