I'm really new to all this so any advice from me is just from my very limited experience, so take it for what it's worth.
I looked at a lot of frames too, and I was also looking at that size range.
It warrants consideration for what kind of "real estate" you require for what you intend to install on the frame. In my case, I wanted a hobby-grade quadcopter to step up from the toys, but I want it to be expandable to accept a small camera and eventually (much later) some basic FPV gear. I decided on APM flight controller and two things that really make that shine in my opinion are the 3DR telemetry link with Mission Planner and of course a GPS module. But all those add-ons are pretty much all I think I'll require for quite a long time. Note that I chose the APM for my own reasons and there are several good flight controllers out there to choose from. In other words, I'm not trying to sell you on the APM. It has its pros and cons too.
I ended up shaving away lots of possibilities and ended up with a short list of three.
1)
S500 frame
2)
reptile 500 frame
3)
HMF U580PRO frame (totem)
The reptile frame I liked because of the larger body, allowing for more room for "stuff". But then I realized it had the same arms as the flamewheel which I'll explain below. Also, the body had no integrated power distribution, so that and the legs knocked it out of the running.
The HMF U580PRO is an included retractable landing gear upgrade from the U580 with the fixed legs. This looked like a really nice frame, but since it's nearly 6x the cost of the others I figured I'd maybe consider that for a later build. I figure at my beginner stage, there is a real possibility that I could send this thing through a wood chipper or something and lose it completely, so not investing in a high-end anything was probably a prudent path to follow. You can get budget stuff and still have quite a nice quadcopter. I'd like to have an upscale frame at some point, but I have a lot to learn and I hate the idea of crashing the expensive stuff right off the starting line past the point of repair, and that's a real possibility with my experience level. I'll just forego that choice until I have some decent knowledge and chops.
So that left the s500 frame with the integral distribution board. Truth is, the integral board is a little tidier, but I can't see that a separate board or just neat wiring would be all that much different. It's really a minor thing. But this frame has it and I used it and it is a nice touch. I found that it has plenty of room for what I plan to install on it. The rod mounts under the frame are a nice way to add possibilities and it's included.
Also, and this is the big deal, the arms on this frame have a carbon fiber rod cast through the center of them and that plus whatever material they are cast from resulted in a really stiff arm, which I liked enough before. But once I had the thing in my hand and flexed it in-person, I was really impressed. These arms are really pretty nice and I am a big fan now. Note that apparently there is the same frame out there with blank body plates (no power distribution) and less-rigid arms - be sure you get the stiffer ones. Search around and you may find the softer ones, but all the ones I saw were the "newer" version with the good arms. The way it's sandwiched together in assembly, it results in a pretty rigid frame and I'm really happy with it except for the legs. They typically come with these four fragile, spindly curved legs with hook toes which readily snag on the littlest patch of grass and if you get this frame, I strongly advise to get an upgraded landing gear.
maybe something like this one:
link
So this brings me to the flamewheel arms. From what I've seen and read, those arms are extremely flexible and I'm sure I would have regretted buying a frame with those arms. I've seen a couple videos showing how readily they bend and twist with just a bit of hand pressure. Having said that, they are very popular so I guess they are OK for what they are asked to do. But the s500 arms really are a lot more rigid, and of course the frame is a little larger (actually more like 480 than 500 in reality, but bigger nonetheless).
Good luck in your choices. Remember, I am a total rookie and anyone else who offers advice is likely a lot more learned and experienced. I don't feel wishy-washy about my findings, but I'm sure there are more considerations out there in the wild.
