Pair of Play 1 vs Play 5 sound quality

In my opinion a single Play:5 sounds better as the Play:1 does not have the base response (unless listening from about 2 feet away).

Play 5 second gen. is awesome!

Although the OP/reply are with respect to a single gen 1 play 5, I would say that a 1 pair will still trump even a gen 2 play 5 except in the near field where the single unit 5 will still offer a chance for viable stereo imaging via the stereo illusion created in the brain. But that illusion will collapse while remaining present at further distances in the room for the 1 pair, as long as each 1 can be kept at the same distance from its partner unit. So for the usual listening distances in a room, the 1 pair, with its stereo sound will sound better to people that have exposure to stereo. On the other hand bassheads that don't need the stereo image to perceive good sound quality will prefer the 5.

If you have the budget and the space/room, a pair of Play5s sounds great. However a lone Play5... I prefer a stereo Play1s or Play3s.

It's such a subjective thing, depending on the type of music and the person listening, and their personal preferences. There's no single correct answer. Everyone who has replied is correct. For them. You have to make your own choice.