Monitor Audio Platinum or Magico A3

It’s more relevant than " having heard the original flagship MA Platinum speakers", because the OP asked about Monitor Audio Platinum IIs and they are voiced differently than the original Platinum series. I didn’t opine on the Monitor Audio PL300 IIs that the OP mentioned because I’ve never heard them. I mentioned I have the PL500 IIs because they are voiced similarly to the PL300 IIs. Monitor Audio and Magico have a different sound. I’ve listened to Magico A3s on two different occasions and they sound totally different based on the other components in the system. The bottom line is the OP, if possible should try to listen to both speakers with his own amplifier and preamp. If that’s not possible he should use his own ears to decide. I’m not a fanboy of any speaker, including Monitor Audio. I would be naive to believe, because I prefer them, they are right for everyone. There are no absolutes in audio, only preferences.

Speakers are about personal preference. I own Monitor Audio PL500 IIs and have compared them to Magico S5 mk2. I still have the Monitor Audio PL500 IIs. You really need to listen, but remember the other components can drastically affect the overall sound. 

Eric that is interesting.  In terms of audition I  have had two auditions of the Magico A3.  But the Monitor Audio Platinum II would be a blind (or is it deaf) buy.  
The reason I say that is interesting is that I would have thought it would be the other way round - because of the port.  The MAs are ported and the Magicos are not.  I thought that ports, in particular rear ports, needed the space behind the speaker (unless one wanted to get some sort of boost by actually being closer to the rear wall / corner).

Lots of variables, as I infer from your reply.  One interesting factor is that the Magicos are stunning looking in the flesh, whereas they look like boring boxes in photos.  Size also counts, as do specs, and I also value the opinions of others.  

Magico tends to make their speakers for rooms where there is lots of space to the sides and behind. 

Monitor Audio for smaller rooms with more restricted listening locations. 

This is by no means the deciding factor. You should listen for yourself, but if you listened in the store and thought both were equal, I'd consider the room. 

Best,

E