Just one?
The Incon turbo kit I used on my Mustang awhile back had two T25s - I never pushed it past 10lbs of boost but I know it could've gone further. The T25 used in mine was a JDM unit like what's found in the 300ZX I was told but could never confirm for sure. These turbos were supposed to be small for fast response (boost right off idle!) but together could supply the amount of boost the kit was rated for.
IMO just one 300ZX turbo won't cut it. In fact an upgrade for the kit I used was some sort of hybrid T28 turbo. I think 10lbs on a 5liter motor from a single small turbo is too muxh to ask.
As for 10lbs being the "same" - yes and no. Same amount of pressure but the belt driven unit has higher parasitic loss and cannot make full boost until max RPM is reached. The turbo on the other hand can make a set boost over a wider RPM curve. The belt unit suffers losses from slippage (don't use a cog on the street) and when you change altitude the belt unit cannot compensate like a turbo will. Same with changing manifolds and heads etc. - the belt unit will lose boost as intake\exhaust effeciency goes up - the turbo just compensates via the wastegate.
The disadvantage to turbos is space\packaging, heat, and complicated plumbing. The advantage is better power production overall. The belt unit's big advantage is packaging and simplicity. I now have a supercharger on my Mustang since the turbo manifolds wouldn't fit the bigger 351W (shrug). Should've put a turbo 302 in my Datsun Z instead of the 383
BLKMGK.com
Clear as mud? Turbo is better but more complicated.