Hydraforce 3-way valves are twice as expensive as Pollak 3 way valves.
The main advantage of using Hydraforce valves are that they are designed to withstand higher working temperatures. This is not surprising since Pollak valves are engineered for use as fuel valves and Hydraforce valves are engineered for use as hydraulic valves.
So...if your conversion configuration does not expose the valves to high temps using the less expensive Pollak valves is a wise choice. If the configuration DOES expose some of the valves to high temps it might be wise to use Hydraforce valves in those locations.
I have never had a failure of a 3 way Pollak valve but I ONLY use them where they will not be exposed to fuel temps of over 100F. And there HAVE been some reports of Hydraforce valve failures due to polymerized VO causing them to stick in an open or closed position. It is probably the best policy to engineer/design all conversions using a configuration that avoids exposure of ANY solenoid valve to high temp fuel. And if a conversion is engineered that way I don't see any reason to use the higher cost Hydraforce valve.
However..sometimes it is neccesary to place a valve where it may be exposed to high fuel temps. In this case you MAY be able to use a Pollak valve if you wire it so it is in the "off" position when on VO. When powered solenoids (the part that moves the valve mechanism) run at higher temps. So if the solenoid portion of the 3 way valve is NOT adding heat the valve when hot VO is passing through the valve may never fail. If it does a you are faced with the decision of replacing it with another Pollak valve at half (or less) the cost..or a Hydraforce valve.
I think the reason that the Pollak valves got a "bad reputation" was due to the fact that Frybrid uses Hydraforce valves and Chris tends to spread FUD about any component he does not use in a marketing effort implying that all other conversion are inferior.