In the AV's so far...

Alliance does not know if the horde is in Galv until they go into the building.
So there is enough of a head start for the horde, that even if the alliance go straight to Galv with Crusader Aura the whole way, you have no clue if there are zero, six or twenty horde inside; going by this AV weekend, the average is 15 or so guarding Galv.
The horde have to have more than a 10 second advantage in reaching Galv.
Galv is also much tougher than Belinda... with ten alliance in Belinda's room, twenty horde will win almost every time... I like to Cyclone the tank and or healer, then Tranquility x5... then go kitty and kill whatever.
If the alliance has twenty in Galv's room and there are more than 5 horde defending him, enough of the attack is dead that the game becomes an auto turtle.

The alliance bridge is easily easier to defend than the Frostwolf area; there is a breech where you can run around and not even be hit by either of the towers.
That said, it works both ways; if I stealth to Frostwolf and cap RH and both towers.. I cannot guard a single choke point and know there are no horde behind me... if a horde manages to get the last alliance graveyard and both bunkers capped, they can stand on the bridge and know with 100% certainty that no one is sneaking past them.
When I was doing AV's with Shammies.. the alliance bridge was so fun to defend with staggered Thunderstorms; the horde don't have anything even close to that..

So the alliance has a huge advantage in holding their base, and a similar disadvantage at holding the final horde base once it has been assaulted, assuming the horde backcaps which is extremely common in these games.
And the horde has the initial advantage of Galv being much tougher than Belinda.

AV is still one of my more favorite BG's, probably a little behind AB.