I expected a similar SoC specs to the Lumia 520, because the price is also close. But the CPU in the Lumia 520 is twice as powerful as the cpu in Nokia X.
In the press Nokia is calling it Dual core Qualcom snapdragon, giving the impression that it is similar to the low-end Lumia phones, but it isn't. the SoC is something where they cut costs.

It will be interesting to see just how low the price of Nokia X will go. The Lumia 520 started at 179,- euro here in the Netherlands and currently is 119,- euro (no-branding, simlock-free, including taxes and Nokia rebate). Prepaid versions are cheaper (99 euro), and I read that in the US the AT&T and T-mobile prepaid versions are even cheaper than that.
At those prices I think I would recommend the Lumia 520 to these Nokia X phones because of the low-end SoC.