Many people assume that broccolini and broccoli rabe are the same, but that is not true. Broccolini comes from a completely different family than broccoli rabe. Broccolini is part of the cabbage family, while broccoli rabe comes from the turnip family. Broccolini is a milder vegetable, and it is closer in taste to regular broccoli. Broccolini is said to be the cousin of regular broccoli and Chinese kale. Broccolini has broccoli florets, long flimsy stalks, and green leaves.
Broccoli rabe has a bitter flavor, stalks that are a pale green color, and turns into yellow, and it is a popular Italian vegetable. It has a rather delicious taste with it being a bit peppery. The leaves also have a pleasant flavor, and when compared to broccoli, the overall taste of broccoli rabe is of higher quality. Broccoli rabe is often seasoned with garlic, and if you were eating it in an Italian restaurant, it would be fresh garlic. If you tasted both of these vegetables one after the other, you would be able to tell the difference.
One thing that you should know about the broccolini is that this is a type of hybrid vegetable. This is a cross between broccoli, which a lot of people are familiar with and Chinese broccoli. This is a rather new vegetable because it was only created in the early 90s.
When you say broccoli rabe, this is a type of vegetable that is known to be leafy, but the leaves and stalks are going to be tender. Take note that this is also going to be less bitter as compared to the typical stalks of the broccoli. There are some types of broccoli rabe that are going to be sweeter than others. It is all about choosing the one that will work best for the dishes that you want to create.