I've done a little bit of experimentation with this, comparing real B&W film to various software's conversions to B&W. Most interesting was a case where I took a picture of the NYC subway diagram with a red filter. I could never make the RGB data from the digital camera look like my original negative, even when shooting through the same red filter. (Which should not be necessary, if you want to block blue and green, you should be able to do that in software. Lightroom, at least, did not let me make a matching image.)
More subjectively, I think most digital pictures converted to B&W look kind of dull, whereas actual film looks very exciting to me. I haven't done any detailed research into this, but I'm not 100% convinced that collecting luminance through red, green, and blue filters can capture all the data that panchromatic B&W film captures.
(Even more of a tangent, one of the joys of B&W photography is that you can outright lie about colors and the photo still works. Try a red filter and watch the blue sky become black!)
More subjectively, I think most digital pictures converted to B&W look kind of dull, whereas actual film looks very exciting to me. I haven't done any detailed research into this, but I'm not 100% convinced that collecting luminance through red, green, and blue filters can capture all the data that panchromatic B&W film captures.
(Even more of a tangent, one of the joys of B&W photography is that you can outright lie about colors and the photo still works. Try a red filter and watch the blue sky become black!)