Stoves are a topic of great interest to me. I have owned about 8 of them, and I have done more than just own them, I have actually refurbished a few of them. I have includes some pictures of a real rescue job I did on a whit field advantage.
With that in mind I currently own a Harman P61A, and it is the stove that I observe pellets from. The P61A is not the most visually pleasing stove on the planet, I in my experience it is simply one of the best stoves made, including in Harmans line up. The other Harman P models are also very good, and rather similar in many ways.
In a top feed I found that an inferior pellet like Appling County can work really well because the ash is much lighter and just blows out of the burn pot. The downside to Appling is you will need to empty your ash pan after 5-10 bags. Now some top feeders like the St. Croix add one useful variation on the top feed approach, and that is to have a plate on the bottom of the burn pot that rocks back and forth to prevent cakes from forming.
Other stoves are very sensitive to saw dust, that is a common issue with some of the Englander stoves and there dual auger feed system. Other stoves are very sensitive to long pellets, and get jammed because of them. Once you learn what works in your stove you need to take that into consideration when selecting a pellet.
*** Important- It is easy to fall into the thinking that the best pellet is the one with the highest BTU output rating, that is not a good way to select a pellet. Firstly many of those ratings are bogus anyway because many pellet manufactures use a variety of wood types, and that BTU rating can vary from batch to batch because of it. Manufactures do not test every batch, and some manufactures are most conservative about there ratings than others. In my estimation BTUs are not a number I would even look at.
A stove burning cleanly a lower BTU pellet will produce more heat than a stove burning with issues (feed problem, jams, clogged burn pot, ect...) a higher BTU pellet.