There are technical differences in terms of the amount and nature of the filtering in the Puritan vs. other devices like AQ. AQ has a unique grounding system and is at its best when everything in the system is AQ. This is not the case with puritan and it is cable agnostic though their Ultimate XX PCs are excellent for the money.
I like the PSM156 in general, its price makes it even more appealing. I like that it is available and in-stock domestically. The one unit I think I might like better is the Inakustik but at that point it is a matter of taste.
I would be shocked if you are not happy with it.
Full disclosure, I am a Puritan and AQ dealer and am planning to buy into Inakustik so I certainly am biased toward all these brands. A Niagara 3000 with thunder and/or tornado PCs through the system will beat it but that is a lot pricier.