Another vote for Helms Deep being superior to the siege of Gondor. It feels more claustrophobic and draws you in that little bit more.
Other issues I have with the Gondor battle (which I nonetheless enjoyed) is the death of the Witch King on what can only be described as a technicality, and a massive invincible army of the undead turning up at the end and overcoming everyone, leading you to ponder what the point of all the preceding action was.
I'm enjoying Bad Wigins' nitpicking at the realism of the cavalry charge in the context of a battle which is ultimately won by a load of glowing ghosts. Maybe they're just magic horses, dude.