While I'm mostly off the W/xEldrazi train now, I don't think I'd run this over a Battlefield Forge/Plateau. I like the ability to cast noncreature White/x spells in an Eldrazi deck, and finding colorless sources has never been a serious issue for me (finding the right quantity mana at the right times has been a lot more frustrating). I'm not sure I was even on 4 Cavern before.
If there was a creature that made me want to run a third color, this gets a lot more interesting. Since I've never even considered a 3rd color before, it's possible this creature exists already as I've never looked for it.