Let’s start with the correct product names.

• Play:5 (Gen1)
• Play:5 (Gen2)
• Five

There is no sound difference between the Play:5 (Gen2) and the Five. Both are a sound improvement over the Play:5 (Gen1)

The Five also has faster processor, more memory and a better wireless radio.

The Play:5 (Gen1) is S1 only. The Five is S2 only. The Play:5 (Gen2) can be used on either system.

Again, there are no PLAY Fives. There are 2 generations of the PLAY:5, and one generation of the Five. 

If you have the PLAY:5 gen 1, then yes, I’d say there’s a significant sound upgrade from the PLAY:5 gen 1 to the Five. And whomever you gift the older PLAY:5 gen 1s would certainly continue to use them on an S1 system. 

Thanks for your helpful advice.

@Devonian .  Given your continuing confusion over the names and generations of these speakers, are you sure that what you have is a Play:5 gen 1?  Does your speaker have touch controls that you tap or physical buttons that you press?  Does it have a line-in socket AND a headphone socket or just a line-in socket?

As @Airgetlam says, you would definitely notice a difference.  Or, if you didn’t, you are not fit to own Sonos speakers .

But no need to take our word for it.  Sonos offers no-quibble returns in most if not all of its markets, which means there is no risk in trying for yourself.

Are you saying there are three versions of the Five.?  Play 5 Generation 1, Five and Play 5 Generation 2?  I thought there were only two versions?  I have Play 5 Generation 1 so if I have understood you correctly there would be a significant improvement if I upgraded.  Do you know if my Play Fives Generation 1 would work independently as a stand alone speaker?

There are 3 versions.  Play:5 Gen 2 and Five (3rd generation of the speaker, but not referred that way by Sonos) are improvements over the Play:5 Gen 1.  The Play:5 Gen 1 can be used on it’s own.

Note that the Five is the only one you can purchase new anymore.  If you were to purchase a Play:5 Gen 2. it would be from a used market.  Obviously, your results may vary.

As @Mr. T suggested, there is one version of the Five, and two versions of the PLAY:5. 

The Play 5 Gen 1 would work as a stand-alone speaker as mentioned above, BUT only using the S1 controller. Your other Sonos would use the S2 controller.

Yes, they have all these features, definitely Play 5:Gen 1s

It depends what you mean by 'these features'. My post didn't say which features belonged to which speaker.  But perhaps ypu can tell from @jgatie 's images. 

I should have said that the features are exactly as shown in @jgatie’s image.  So in short is it worth me spending about £750 upgrading these old speakers to Fives taking advantage of the 30% discount or would I not really notice the difference and if I give the old Play Fives to a grandchild and they have the Sonos 1 app will they be able to use the old speaker with no further Sonos equipment?