@FlyingDice: gotcha on what you were saying, but I don't really think that was the point that Cruxador was going for.
Cruxador's main points seemed to be:
1) there's less gender difference in the romcom novel market in Japan than in the West, so you get e.g. "dude versions of 50 shades" in Japan.
2) manga is more niche, so it's more quality driven than LNs.
@Culise, thanks for printing the figures.
What I did further with those, was to look up the number of volumes each series released per year, then divide 1 years worth of sales per series by the number of volumes each series puts out. That gives a good "per volume" estimate, which shows the most popular mangas outsell the most popular LNs by a decent margin (around 3 to 1). Basically the highest selling LN volume sold about half a million copies, and the highest selling manga volumes are around 1.5 million copies (not counting serialization). Both LN and manga sales slump off at around the same rate (the top manga series sold about 10 times the volumes of the top LN series, and the 30th manga series sold about 10 times the volumes of the 30th LN series), so it's not a case where a handful of super-popular manga artificially spike the sales: they really do sell more manga than LNs by a goodly margin.
Manga are ahead on both sales-per-volume (how many people bought it) and total sales (which includes people who buy a whole series). And that's before considering those people who only read mangas in serialization.