The only way I know how to differentiate this caterpillar from the Tomato Hornworm is by the color of their “horn”. If black, it is the Tomato variety; if red, it is the Tobacco variety. This caterpillar is pretty big and I’m betting on it being the Tobacco Hornworm. Cute caterpillar:>) The horn here is red.
They are considered pests of the plants in the nightshade family or Petunias, too. We do pick hem off our tomato plants and try to find something wild for them to chow down on, like nightshade. More often than not we see the eggs of a Braconidae wasp on the more grown up caterpillars, so many do not survive to adulthood in our area.
Here is a bit of a write up on them:
Taken with an Olympus FE240 set on macro