Im confused by some of the above comments about measured pressure.
Rated pressure for these pumps is inverse to air flow. Max flow occurs at min pressure(ie. with free-flowing air unburdened by tubes, tanks, or air manifold). For example, the paralleled dual outlets of Rena 400 are claimed by the manufacturer to produce 4 psi max. Under full load-- with a pressure gauge placed at the end of my 20' silicone hose whose output is stopped up at the outlet to block air flow to zero-- my Rena 400 produces 3 psi max. After connecting the hose to the Terminator air manifold, max measured pressure drops to around .3 psi. Then with the Renas output adjusted downward to the point of obtaining the minimum pressure required to prevent skipping(which is Vics recommended set-up to minimize turbulence) measured pressure falls to around .1 psi.
However this is not the way that I measure or regulate pressure. I position a high-quality brass needle valve close to the Terminator air manifold, downstream of a co-located 5 psi Wima dial gauge. This way the dial reads the back-pressure behind the needle valve instead of pressure between the needle valve and the air manifold. With the Renas outputs turned wide open, the dial now reads across the full sweep of 0-3 psi. As the needle valve is opened up to introduce flow to the tonearm, the pressure drop below the base line of 3 psi measures the pressure lost through the manifold to float the tonearm slider. The minimum pressure drop required to prevent skipping is 1 psi. This is indicated on the dial as a drop from 3 psi to 2 psi. Simply put, it takes 1 psi of pump pressure to operate the tonearm.
Why is this significant? First, it demonstrates that a pump with a 1 psi output is necessary and sufficient for Terminator. Second, it demonstrates that the Rena loafs at one-third of its capacity in this application. A higher pressure or higher flow pump need not apply. The only remaining meaningful variable is the smoothness of the air flow.
Its conceivable that the Hi-Flow pump pulses less or that a leaky flow tank with cotton balls inside further smooths pulsing. Other differences may include the quality and positioning of the pressure regulator. I can hear the difference in turbulence between a smooth brass needle valve and a cheap plastic aquarium valve. I like positioning the brass needle valve as the most downstream link in the chain. This might help filter pulsing of the spring mechanism of the upstream dial gauge.
I may try the Hi-Flow pump, but am first inclined to add more and larger smoothing tanks-- only a gallon plastic can so far. There seems to be a wide range of opinion in the fish community about whether the Rena is loud or quiet. YMMV. There is a youtube video of a guy quieting pump vibration down considerably by hot-gluing the pump motors to their chassis mounting points. I may try this.