Watcher's Keep in SoA or ToB? Options

[coaster]

Hi

I'm coming to the end of SoA and would like some thoughts on whether to tackle Watcher's Keep in the SoA or ToB portions of the game.

I was originally going to do WK in ToB, because I want to add Sarevok to the party, and enable him to share in the huge amounts of XP available in WK. But most people here seem to have gone to WK in SoA. Is there some reason for this? Will I struggle at the end of SoA without some of the upgrades I might get in WK?

Thanks

coaster