Once the fruit reaches the "blush" (aka breaker stage) it gets nothing more from the plant. Nothing is gained by leaving the fruit on the vine past that point. And much is potentially lost - splitting, cracking, watered down taste, damage from pests, injury, rot, etc. So you'll find that most experienced growers pick at that stage rather than leaving on the vine. But the breaker stage is not the same thing as picking a green tomato.
http://postharvest.ucdavis.edu/pfveg...=30014&a=83755
Really no such thing as a "vine-ripened" tomato as 9 times out of 10 when it is finally picked it is actually an over-ripe tomato.
Dave