That depends on a number of things including your alignment, wheels, etc which can through off numbers on a roller dyno vs dynapack.

In my skyline, I put down 382awhp on an AWD dynojet. I put in a B&M new volt, and a cat delete, and ran 394awhp on Mastros Dynapack. A gain of 10+whp for those two items would not be unreasonable. Temperature was about 15 degrees cooler for the first dyno. So unless you are running really heavy wheels and a bad alignment, you probably wont see that huge of a difference between the two types.