Using a boost controller doesn't guarantee that the boost won't fluctuate. It really depends on the quality of the rest of the set-up and how much you are asking of it.

For example, if you only have a 7psi actuator and you want to make 25psi, the controller will struggle.

The Profec-B is a simple, no-frills, good quality boost controller, but don't expect it to work miracles. It mainly makes it much easier to control boost from inside the car, however, it will be more accurate and stable than a bleed valve.