funny thing is, I used to have exactly the same opinion as Tomahawk expresses here, take either 10 or 25.
But strangely enough, I'm now running 15 with St&Mu for 90 points, and I actually like them!
10 without a standard is something people just ignore. They can't even flank stuff without getting beat up!
But 15 with standard looks like a real unit, and people treat it as such. They are scared of being charged by it, they cast magic at them and they send expensive units to go kill them (much to the amusement of my knights
), .
Seriously, I have seen huge infantry blocks run after them, the best example being a 15-strong unit of White Lions
that spent half the battle chasing them! And since those guys were the only thing stopping me from riding down the rest of his units, that actually won me the game.
I know that 25 makes for a better MBU, but for the distraction and flank guard purposes I use them for I don't think I can justify another 50 points.
cheers,
martin