I have not flown the Hawk yet, so I can't really speak for it, but I would wait on the Hawk until it gets updated with an EFM. For now it still has an SFM so the flight model will feel like something from Lock-On.
The Huey is currently my favorite helicopter in DCS. The systems are relatively simple compared to the A-10C so I can focus more on enjoying it and less on remembering how everything works.
The Huey is only effective in combat against soft targets. With AI controlled door gunners on each side, you can rain destruction on enemy infantry and trucks. You can also take out some of the lighter armored vehicles, but it is almost impossible to take out a T-55, so don't even bother with tanks. The Huey is very vulnerable against anti aircraft. You have flares but no laser or missile warning system so it is best to avoid anywhere with known air defense.
The Huey also has the nice option in the loadout screen of removing weapon pylons, which gives a more civil aviation experience. I like to fly around in the included NASA paint scheme like this.