Having owned the PG500 for about 18 months, I can tell you that I still absolutely love the grill. However, having never owned a Memphis, I can't really compare it directly to one of those...
PG500's direct grilling area is wonderful but I suppose somewhat limited, but then all pellet grills are similar in terms of the size you can 'grill' on, in many ways the size of direct grilling is probably larger then most. The biggest advantage of the PG500's direct grill area is that it's always there, ready to be used , all you have to do is crank up the temperature let the pellets feed in faster, and it gets hotter and hotter... it's capable of at least 1000F in that direct grilling area. Of course , having that area dedicated to direct grilling, also means you loose some area for doing other things that aren't direct grilling... so there is some trade off. But, IMHO the Fast Eddy pellet grills are second to none when it comes to direct grilling..
Then of course... because of Fast Eddy's patented design, you get the ability to easily do 100% indirect heat cooking too... I don't think any other pellet is truly capable of the kind of indirect heat cooking that can easily be done in the PG500. Now this may be just splitting hairs to some degree... but if I want to, I can cook with indirect heat at well up into 500 degrees, or even hotter if I want ( rarely do I want, except for Pizza maybe )... but you could easily run the PG500 at 400F with a roast, or a turkey, or chicken, or whatever on the indirect side, and there is virtually no chance of a grease fire. You try that on nearly any other grill, and there will be some risk of grease fire as greases drip off the food and onto a drip tray that's usually significantly hotter then the temperature where the food is at. Yes, of course there are ways to avoid grease fires on other grills, like maybe having a drip pan, or something to catch grease before it drips on the grill's drip tray... but with PG500, the drip tray never gets above the set temperature... So, just like with the direct grilling area, this indirect area and how it operates with virtually no radiant heat is not always a 100% positive thing.... but for me it's pros outweigh it's cons...
So, on a more traditional pellet grill, you can use radiant heat to your advantage in some situations... Like , well lets say you had a whole bunch of chicken wings... You could likely set a traditional grill to about 350F, and spread wings out across most of those grills main grate, radiant heat would make the area cook a bit hotter then the 350F set temperature, possibly making the skin a bit crisper... but for sure you would be able to cook a lot more wings on something like the Memphis , then you could on the Fast Eddy... well sort of... On the Fast Eddy , to compensate for the lack of radiant heat, you'd probably need to run the grill at 400F or higher to get that skin to really crisp up quickly... and the good news, is you could do that on a Fast Eddy and not have much of any risk of grease fire on the indirect side...
Anyway... I won't or, can't really say anything bad a bout a Memphis grill... and I have no experience in using one, so I can't really say for sure if they would work better for you than a Fast Eddy pellet grill. All I know is I love my PG500 and don't think there's a better grill out there for me... Other then I do fully admit to using my GMG Davy Crockett alot... for things like chicken wings, brats, even burgers...
Oh... I treat PG500's indirect side much like a vertical smoker... I'll stack racks of jerky, pork belly bacon, canadian bacon, etc... and smoke at temperatures of right around 170F... this works great... I wish CookShack would make a rack system that fit over there... and made it a little easier... but I really love the indirect cooking area of the PG500 for stuff like this. 90% of my cooking in the PG500 is done on the indirect side.
I haven't done much of any 'cold' smoking... so I can't really say too much about that aspect of the PG500... It probably does a bit better at that sort of thing then some grills, but... well, I feel if you really want to cold smoke, it's best done with a smoke source that is not coming from the firepot of a pellet grill . I consider true cold smoking to be bellow 80F... Anything between 80F and 150F, I consider warm smoking, and I jut don't do much of that... This winter I'll likely dabble in some cold smoking, but in the summer, I just find it very impractical... I could warm smoke in a PG500 during winter months very easily...