A soft soap (plastic hand pump) dispenser is currently in my bathroom mainly due to its smaller footprint and more tidy appearance.
My concern is with the amount of wasted soap that goes down the drain. I think it is partly because of using a cheap inferior formulation that clumps more easily and squirts through one's fingers instead of creating lather. I am not concerned about trying to save a few pennies in soap cost, but with the potential load at the sewage treatment plant and making its way into the environment.. at least when compared to using a hard soap. I realize one home has little impact, but if my situation were multiplied it would be like pouring bottles of soap down the drain.
Pump liquid for hand washing mostly. When I refill them I cut them with water as they dispense easier and cuts down on wasted soap as well. My wife thinks I'm nuts but I prefer the thinner consistency and there are little / no drips this way also.
Interesting idea about thinning the liquid soap to improve its performance, though I think the inferior soap I bought might not stand to being thinned.
Before changing brands or going back to hard soap I will try the foaming soap idea...I had positive experience with that in public restrooms.