Let me clarify... I meant more comfortable in the sense that there is less bite on the ball with the thicker string, so a smoother feel ...so more comfortable. (A fairly esoteric aspect of feel, I admit...
)
More noticeable: Thinner strings
will typically feel less stiff and more resilient than thicker, and in that way, provide a more comfortable stringbed. I think that's probably what you meant by the sponginess that thinner provides, yes?
Thicker at the same tension provides less power than thinner; it stretches less when the ball hits (it's more stiff) and bounces back less and slower (less resilient).
Hope that's helped. I'm quite open to more expert opinions on this as I don't consider myself an expert by any means.