The 30 does give much more torque off boost. If someone will let you take a drive of one, you will be surprised how much nicer they are to drive off boost.
Spool wise, my 30 brings my GT35R (0.82 rear) onto 1psi @ 2300rpm in 3rd or 1psi @ 2000rpm in 5th and you get 15psi at 3500rpm.
There is no replacement for displacement if you want to get a turbo on boost nice and early.