They actually do offer both options and Yes I have driven a car with open dump tubes, I have one. Ive been driving w/ open dump tubes to atmosphere since May of 04.... I think its beautiful and sounds great, IMO. "To each his own" right?

For sure. With my last setup, I could live with it if the wastegates opened at full throttle only, but it made considerable noise at part throttle boost when cruising under load in certain situations, which was tiresome.

Hmmm it seems what MechEE implies makes sense about the HP being more directly related to the stress on the engine not the boost pressure. Any confirmation/denial for that? So a SFR TT that made 500 hp at 1 psi boost would cause the same stress as a ACME TT that made 500 hp at 20 psi boost?

There are other factors that lead to increased stress like higher peak combustion pressures and higher exhaust pressures for the same power level, but my point was just that stress from 7 psi at 400 whp isn't the same as that at 300 whp, it clearly is more in general for a well tuned setup.