Why is it that critics love the Decemberists who they always compare to Belle and Sebastian yet they loathe Camera Obscura for sounding like Belle and Sebastian?

Because critics are hypocritical idiots. Same reason why some critics tried to deride Devendra Banhart's Cripple Crow for being overlong and self-indulgent yet they LOVE Sufjan Stevens' Illinois when both albums have the same number of tracks and approximately the same running time. It's all part of the bandwagon I guess. Go figure...