Dragons vs Balrogs

Not just a creature of flesh and blood, then, but a creature of great physical strength in which the evil of Morgoth is housed as a living flame.

Glaurung was only alive and independent of Morgoth because of the latter's will and power. The evil spirit that dwells within him was this will and power.

That would be true except for one thing. Morgoth's power has gone into dragons. They aren't just creatues of Arda, they have been lent the immense power of the mightiest of all the Ainur.

Morgoth's power went into them in order for them to really be, as a result they have a particular 'magic' of their own. But the Valaroukar were already naturally a part of that Unseen Realm, they themselves as Morgoth were there before Time began, incarnation for them in the beginning atleast were as clothes, and truly they were spirits, unlike the Dragons whose bodies were the houses of the will of the greatest of those spirits, that which allowed the houses to continue. The bodily form of the Balrogs like the rest of their Race was a testimony to their personality, the shape of the Dragons came about through Morgoth. By your reasons the Dragons become greater than Sauron.

In the War of Wrath, its the onset of dragons that almost turns the tide against the host of the Valar after the Balrogs have already been virtually destroyed.

It is not really a good idea to use such examples because those Balrogs belong to the older mythology. Tolkien's final word about it was that there were actually only seven Balrogs altogether, which never touched the narratives. The Balrogs you hear about in the Quenta Silmarillion are echoes of those of The Book of Lost Tales. Christopher Tolkien just used the old texts when there was nothing else, and cut out all the stuff he could that was at variance with the new conception of Balrogs, without radically altering what his father wrote or completely eliminating it. So in the texts Christopher Tolkien had to use you get thousands of man-sized Balrogs as cavalry riding into battle, while Tolkien's intention was to have seven great mighty Balrogs, four of which by the time of the War of Wrath had been destroyed, one of which was to survive into the Third Age.

The result is that details about the natures of Balrogs are pretty much vacant, but there are Balrogs, and lots seem to be there and lots seem to get destroyed.

I just read Captain Stern's post. Looks like he covered this in shorter form, but no less precisely.

I think Dragons are closer to Eagles than Balrogs.