Explanation of valuation discrepancies between different providers

Hi everybody,

I noticed that the overall valuation of stocks in Seeking Alpha is completely different from the valuation results of other providers (e.g. GuruFocus). For example, the current top 3 stocks in SA (with a Quant rating of 4.99 out of 5) are valuated as total rubbish in GuruFocus. Also, top stocks in GuruFocus have low/average Quant ratings in SA.

I'm just wondering why I'm finding so many discrepancies between these two providers. 

I understand that defining the potential of a stock is more art than science, but how can the same stock be considered super-profitable and significantly undervalued in one place and financially distressed and significantly overvalued in another place at the same time?

Which one is more reliable in your personal experience?

Thanks for your help