Hi George,
As pointed out by David, many of the performance gains brought by 802.11ac W2 are not supported by most mobile devices and also are not achievable in real-world deployments. However it doesn't mean W2 APs are irrelevant. They benefit from higher performance hardware (RAM, processor) and more refined radio technology, which will help in a high-density of users (HD) deployment.
I agree with David's suggestion to consider the R510 or R610. Also the R600 has had a pre-announcement for End-of-Sale.
If possible I'd recommend a higher quantity of lower-spec APs. If possible don't try and cover a large amount of clients with few high-spec APs, it may be better to have 4 x R510s (one of which with 2.4GHz disabled if the APs are in close proximity to each other). This will result in less load on the APs and an element of resilience should you lose connectivity to an AP. Of course it all depends on the physical deployement! My suggestion above relies on the clients being evenly spread around the venue.
When considering multiple MIMO streams (2x2:2, 3x3:3 or 4x4:x), even if your mobile devices don't support more than 2x2:2 (most are 1x1:1) then Ruckus has PD-MRC technology which will bring performance enhancements when using more spacial streams.
A note on your comment on AES encryption. Ruckus APs do this in hardware and there is no performance impact or limitation. Unlike, for example, an AP doing SSL in software, which is processor intensive.
You mention 802.11ax and R720 - I assume you mean R730 as this is our current 802.11ax capable AP. If your budget extends to using R730, then it would be a great choice as it sounds like you have a high-density of users and when 802.11ax is available in client devices it will bring big benefits to HD deployments due to improvements in spectral efficiency. Check out our videos here:
https://www.youtube.com/watch?v=JtiP0Ry9DHA&list=PLwZotTMbkZQG61ZyQkjsYugb1aeDR5lne&index=1You may need to consider multi-rate gigabit Ethernet switches if you deploy 802.11ax APs to future-proof the deployment.
Finally are you sure a ZoneDirector is the correct choice for the controller? If APs lose connectivity with their ZD they will go out of service and a pair of ZDs would be recommended for redundancy. I would recommend investigating Ruckus Cloud managment, SmartZone 100 or vSZ management. Both Cloud and SmartZone platforms offer site survivability for the APs in the event they become disconnected from the controller and do not need to be installed on local premises.
If you let me know where you are located, I'd be happy to put you in touch with a local SE who can assist and introduce you to an appropriate Ruckus partner in your area.
Best regards,
Darrel.