I decided on the spur of the moment (after I took the photo) to use my Pro 48 along with Mr Pomp. I mostly was motivated to compare the brushes, but the alluring fragrance of Organism 46-B was also a factor: by spending twice the time in lathering, I could enjoy the fragrance twice as long.
Both brushes made excellent lather, so performance is top-notch for both. In feel, there was definitely a difference: with the knots engorged with lather, Mr Pomp felt very soft and very smooth on my face. The Pro 48 was also soft but have a little (very pleasant) grain. Both felt fine, but had different textures. Assuming high quality, a paté and a steak are both very tasty, and both have pleasant mouthfeel, but the paté is smooth and the steak has some grain. The difference is analogous to that.
Three passes with the Baby Smooth — particularly with the extended lathering — left my face perfectly smooth. IMO, everyone should have a Baby Smooth in his razor collection — but I do recognize YMMV and that for some it probably does not work so well as it does for me. I find it one of the best razors I own: reliable, completely comfortable, and highly efficient.
A splash of Organism 46-B to carry me through the day, and the weekend is dead ahead.
BLADE NOTE: The Eldest pointed out an interesting investigation of blade sharpness, specifically directed at the question of why a hard knife edge becomes dull when cutting something much softer. The article is unclear on what is meant by “blade angle.” Consider a whisker that is perpendicular to a plane. The blade can approach the whisker on that plane, in which case the blade angle would be an angle wrt the blade’s direction of travel (cf. a slant razor). But the blade can also approach the whisker at small acute angle to the plane to which the razor is perpendicular — another kind of blade angle, and that blade approach can also be at an angle to the direction of travel. The paper’s summary does not make clear what exactly is meant by “blade angle.”
Update: See also this NPR article.