My preference, for ecological reasons, is for bar soap, without the anti-bacterial properties.
My second choice is for the foaming hand wash. The reason is simple. With the liquid pump, I find that the soap is harder to distribute over my hands, as the gelatinous-like liquid seems to hide in the nooks and crannies that constitute my hands. The foam, once dispensed and wetted, is lather for the better!
Which do you prefer using?