All from my perspective and experience:
Gemeinhardt:
Robustly and durably made. They vary a bit. A very rare one sounds good. However the rest have a particularly poor design of embouchure hole. This means the tone/volume/response is gutless. If you try to get more out of it then all you get is more "white noise", not increased volume of quality sound. Yamaha entered the scene and left them for dead, in every way. Gemeinhardt rested on nationalistic fervour towards their home-grown product (and in those days there was also a fair bit of post-war, anti-Japanese sentiment), and did nothing about improvement. Their demise was certain, and happened extremely quickly in my country, well away from USA.
Altus Azumi:
If you buy one of these you are probably tapping in to what a number of manufacturers of top instruments are doing, and I have definitely seen it in three Azumis:
Buy a half-decent, professional-style head and put it on a Chinese-made flute.
You pay a lot more bucks than you would for a Chinese flute with an added quality head, so you expect pretty high standards in the flute. However...
For a flute with rolled tone holes, as all but some top professional ones have, it is a bit of a challenge to get those tone holes flat. In the older student Yamahas they did. In the newer ones, no. (BTW I have a way to make the Yamaha ones pretty good in about 20 minutes without removing metal, but it is definitely not for the faint hearted!)
So you rely on the resilience of new pads to deal with it. (Higher models of Yamaha have excellent levelness. I think that is actually mainly what you are paying for in a 300 series... or possibly now a higher series still.)
Azumi attempts to deal with it as follows:
Get a flat standard-type file with quite coarse teeth. (Not even the very good rotating disc files that are used so successfully on saxophones)
File across the tone hole until they are flat. But no, they don't stop there. They keep unnecessarily filing far past that, until the metal thickness, which is already thin after the drawing and rolling process to make them, is now pretty darn thin. And do not polish those file-ridged surfaces? No, You leave them. Job done.
Now, to make the flute fashionable you install extra hard pads, possibly the very unforgiving "Straubinger" pads or similar, so you can do some hyped-up marketing.
But pads do not seal until they are sufficiently squashed that the minute ridge blemishes on their surface are squashed, and until they are pressed into the file grooves on those tone holes.
And because the tone hole faces now have about three times the surface area that they would before the filing, there are a lot of ridges to squash and long hollows to fill.
So the player has to press harder than normal to get a decent seal. So nothing has been achieved. They would have been better left as slightly non-level.
But beginner flute players should not get used to pressing the keys extra hard. If you establish that habit then as one progresses that extra pressure required interferes with playing fast.
goes to the repair technician.
So what to do?
Take it to a technician and ask them to make it work with light pressure. NOw that the tone holes are damaged, the technician has only one choice:
First get rid of the file marks. Then chamfer the edges of the flat tone hole edges so that the tone holes present less surface area to the pad, and polish the new, rounded surface. It is quite a big job, and needs to be done with the utmost care. But there is a thorn in this process...
It involves removing even more metal. There is some risk of unknown degree, that his removal of even more metal will allow the tone hole edge to lose support and completely collapse. That would be a very serious situation indeed, and very expensive to correct, even just for a single tone hole.
Is the owner prepared for this bug-bucks risk?
I, as a technician, being aware of it, am not prepared to cover it, so I will not take the risk. Customer has to live with the extra finger pressure.
I presented all this to a local teacher who was not happy with the finger pressure required on just such an Azumi owned by an advancing student. He seemed to just not want to understand, or perhaps he just did not believe me.
And this is why I cannot recommend such flutes. IMO Altus wrecked them at the factory.
Of course, it is possible Altus has stopped doing this. Who knows?
I have struck the same thing with another Altus model, a Pearl model, and a Haynes model.
BTW it is unlikely that you can see these flattened tone hole edges without taking keys off.
Of course one might argue that the filing had been done post manufacture. In each case, I was assured by the owner that that was not the case.