The poster really didn't make it clear if this was a non or near LOS shot, or LOS. He just said he had trouble "outwards of 8 miles". He also didn't answer any of my questions regarding his deployment... that being said... if we only care about who has the best link margins under identical deployment circumstances...we can create an apples to apples comparison...
PMP320 vs PMP450 - LET'S GET READY TO RUMBLLLLEEEE!!!!!!!!
Let's assume a 10MHz channel width, which both products can do, and will also allow for the maximum 40dBm EIRP. Both system are 2x2 systems capable of mimo-a/b operation, that's a tie. As you mentioned, the PMP320 has HARQ, which is technically a bit better then PMP450's ARQ.. give the 320 a point. The stock PMP320 AP antenna and the PMP450 AP antenna are nearly identical performance-wise, so that's a tie. The PMP320 AP can push out 1.5dBm more power and still stay within 40dBm EIRP over the PMP450 (450 is limited to 22dBm @ 10MHz), so another point goes to PMP320. The PMP320 SM's integrated antenna has quite a bit more gain at 14.5dBi vs. the 450's 8dBi patch, a bunch more points for PMP320. Let's go to the judges for a tally... and assuming we're keeping it above the belt, and we're staying within legal 40dBm EIRP, the answer is... drum roll....THE WINNER, THIS ROUND, BY TECHNICAL KNOCK OUT.... PMP320!!!!
But of course... this is all just math and as I've shown under these conditions the PMP320 is going to have quite a bit more stamina...uhhh.... I mean gain and be able to negotiate links under more difficult circumstances.... but what if we want to see a fight that couples stamina and speed... stay tuned... because that's coming up NEXT!!!!!!
I believe the tables are turned however when you make a few strategic deployment changes. When you add a reflector to the PMP450's SM, you get about 6dBi gain over the 320 SM, and I think a reflector is a pretty typical deployment accessory across the 450 line. In addition, if you run a 20MHz channel width, you can bump the power up to 25dBm (both AP's and SM's). We also use very high quality 18dBi 65deg sectors with our PMP450 AP's. For the coup-de-grace, the 450 gives the 320 a black eye with a much better b/pHz ratio.. e.g. 60mbps vs 40mbps assuming 10MHz channel width. OH yeah, and the PMP320 SM's can't even do 40mbps, they can only push like 18mbps.
This is our typical deployment stratagy, and in regards to the original 'outwards of 8 miles' post, we have no problems doing this shot and getting 6X modulation and 80mbps aggregate link eval's on a 20MHz channel width. I think it's safe to say...
PMP450 IS THE NEW HEAVYWEIGHT CHAMPION OF THE WORLD!!!!
So cheesy boxing analogies aside... In regards to your post concerning non/nearLOS shots, I'll admit it, I don't have a lot of experience doing those kinds of shots because we like to avoid headaches.... that being said, based on my outlined deployment scenario, technically the PMP450 should outperform the PMP320. There's no mystery or magic (or actual boxing) going on here... just math.