To answer your question, there is no clear winner with either brand. It is not possible to say that Sigma is better than Tamron, or vice versa. This is why you are seeing "conflicting" reports. Is it worth paying for the APO version? Personally, I'd say yes, but my needs, priorities, and what I consider it's worth paying for a lens are almost certainly different to yours.
These are relatively slow, relatively cheap lenses. As such, you won't get wonderful performance out of the non-APO versions, especially at max zoom and wide open apertures. This applies whichever brand you are talking about. The APO will give better results, but only you can decide if it's worth paying for.
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