As others have said, the Canopy line is not Wifi but custom FPGA based. And the Canopy scheduler is very, very efficient, which makes things like bandwidth distribution and latency very stable. They've put some of the same ideas into the ePMP product, but it is still an 802.11 radio. We have deployed both Canopy on large scale and ePMP on small scale with great success. It's only going to get better once the ePMP can be precisely synchronized with not only the PMP100 but the PMP450/450i later.
One thing you can do with the PMP450 is zero guard band between adjacent sectors. Say you have an AP on 5750/20MHz. Your next co-located AP can be on 5770/20MHz. Add back-to-back frequency reuse via GPS sync on top of that and it is priceless in congested areas.
Yes, the current PMP450 is limited to 20MHz channel bandwidth, but the 450i is starting to ship now which is a huge step forward for the 450 series.
Here's one of my stories on a migration from Ubiquiti 3.65 to 3.65 PMP450. It's night and day difference. http://community.cambiumnetworks.com/t5/PMP-Stories/Ubiquiti-3-65-to-3-6-450-Migration/m-p/43593 We've stopped deploying all Ubiquiti PTMP gear.