A larger turbo doesn't necessarily mean you'll get more performance at a given pressure, like 14psi. It all depends on the compressor map. With the SP61, 14psi is closer to the sweet spot on the compressor map than it is with the CT-26 (or so I've heard from everyone, I personally havent seen the maps myself). If you were looking at a larger turbocharger, it is possible that 14psi is far enough away on the map that you would actually lose performance over using a ct-26. Like I said, depends on the maps.
As far as the higher efficiency meaning it pushes more air volume , that is wrong. The volume that the engine can ingest is a constant, and is calculated by the VE and displacement, and there is only so much volume in your IC, pipes, etc. What being more efficient means is that the compressor can compress the air at a given volume and pressure more efficiently, as in it creates less heat during the process. Less heat means more air mass (ie density), whcih equals more oxygen molecules, therefor more fuel and more power. To see this lets look at the ideal gas law:
PV=nRT
P=pressure, V=volume, n=moles (mass), R=constant value (doesn't apply to this discussion), and T=Tempurature.
Since the pressure is a constant (14psi, well technically 28.7 because we use absolute pressure), and the volume is a constant, and R is a constant, then all we are concerned with here is n and T.
In the equation, if T is reduced (due to higher efficiency) then n must increase. So the mass of the air increases. And since air density = n/V, so does the air density. This is why you make more power with a more efficient turbo.