as i understand it lowering the comp ratios releaves the stresses of engine componants at a sacrifice of power and torque which can be compensated for by upping the boost pressure.
however if the engine is really well built a high compression ratio can be used and more power can be released, therefore a lower comp engine needs more boost to produce a certain power, thusly the higher comp engine has more power potential and more torque than the lower comp engine.
i used to run a high comp engine on a tt setup and at 10psi it was far quicker than 13psi on a low comp erst engine.
it's mainly cost effectiveness that dictates which method gets used.