Have both of them.
The troll v2 is just as good as any rda for the price point. Easy build, deep juice well, good airflow, multiple driptip sizes included, and well built.
The engine has its merits. Namely, impossible to leak.
But I am an almost exclusive dripper. For me, the engine has a small deck (always gonna be smaller on an rta vs an rda) The airflow only from the top makes it vape on the hot side and does not help flavor. I mainly used it for specific times when I could not drip and needed something that could go in a pocket in a hurry.
My vote is the troll v2. But I will always choose the dripper.