I
love lard in soap. I remember one of the first times I soaped with it- I was comparing a recipe by soaping one batch with lard and the other batch of the same recipe with palm. Needless to say- the lard soap won hands down, no doubt about it. It made such a lovely, creamy/oomphy difference in comparison to the palm that I've been a lard fan ever since.
Yes- there is a tangible difference in a mixed soap- at least to me there is. I find tallow to be harder, slightly bubblier, but less 'oomphy' than lard, for lack of a better term. Or, to put it another way, I find that lard lends a really nice creamy 'body' to my soap that I find lacking when using just tallow in the mix.
However, if you use both (as I am fond of doing on a regular basis), you get what I think is the best of both worlds.
IrishLass