This debate between PMP320 non-LOS and PMP450 non-LOS coverage has been going on for awhile. There was a pretty good thread regarding this where I outlined an apples to apples comparison of PMP320 vs PMP450.
From a technical perspective, assuming that you're running legal EIRP's on everything, the PMP320 should only have slightly better non-LOS performance due to the items mentioned by anthonyw... e.g. HARQ, and more sub-carriers. Aside from that EVERYTHING else is better with the PMP450... much much better throughput, and much lower latency, the user interface and manageability, the future looks far brighter as well.
On the Telrad side... something that a lot of people don't know is the fact that the LTE build they're distributing is only a 2x2 implementation, and it's only 64QAM ATM... which again, side by side comparison, if you're running legal EIRP's... the PMP450 overall beats the Telrad platform when you factor in entry price, ease of management, and overall sector capacity (e.g 256QAM). By the time that Telrad implements 4x4 and/or 256QAM.... I'd wager that Cambium will respond with the next generation platform that will not only build on the PMP450's success, but surpass the competition.