Impression #1: The Ukrainian population is VERY MOTIVATED.
Impression #2: The West will supply Ukraine's population with as much infantry firepower (TOW, MANPAD, etc) as they need.
As the days go on and military supplies flood into the Ukraine from the west, resistance will increase.
Helicopters and tanks will take heavy, expensive, demoralizing losses against well coordinated anti-armor infantry defense forces.
I also think the Ukrainian population will toughen and get trained/experienced in warfare quickly. Potentially Russia is training multiple millions of soldiers on the Ukrainian side with this attack, and forming a national identity, pride, and will to fight.
The only Russian trump card in those situations is air power.
I don't think this is like Afghanistan or the Iraq/Syria smorgasborg. Ukraine is THE buffer state between Europe and Russia. They are fairly westernized. I don't think there will be any concerns with blowback terrorism by equipping the hell out of the Ukrainian army and volunteers/populace. I don't think there are nearly as many policy/cultural concerns about supplying serious infantry weapons to the Ukraine.
Even if all of Ukraine's airfields are compromised, likely Ukraine can continue air operations from Romania and the like. Would the West supply Ukraine with replacement air force? Uh, yeah.
Russia had two military hopes:
1) very fast ground total victory (doubt it at this point, why did Russia attack in winter? Because they could get a quick victory they hoped? Even Russian soldiers will have lower morale in winter operations.)
2) win air superiority to enable a ground victory long enough to get puppet regime in and the West gives up support. I think this is where we are now, and I have NO IDEA how the air war is going.