That is wholly up to you.

Many are happy with the stock system included in the car. It becomes an issue if you want more speed.
Brushed systems are going the way of the dinosaur, but still have their uses, and RTR is only one of them.

BL systems are still out of the reach of many, so if you are about saving a little cash (as we all are in this economy), stick with brushed until 1) your brushed motor wears out, or 2) you want more speed.

Just remember, you may need to upgrade the chassis to take the extra power, and please, please, don't get stupid with KV ratings. For most apps, including drift - 4000Kv is plenty. Any more than that, and you are asking for trouble.