Say you have two cars with the same motor, same internals, same exhaust cat, fmu, etc etc...
and one ran one turbo and one ran another different style turbo
if both wastegated to around 6 psi and hit 6 psi around say 6000-7000 rpm, wouldn't they get similiar readings?

 

If you're talking about air pressure...yes, both will get the same reading of 6 psi. if you're talking about power, no...one turbo might block the exhaust more or heat the air up more in an effort to reach the 6 psi.