Huntsman:
+Excels at medium to short range, where snipers are usually only good for medium to long range.
+Requires 1 second to fully charge, as opposed to 3.3 seconds for the stock sniper.
+Arrows are labeled as a "projectile," the same category of object as grenades, rockets, etc. This means its collision radius is unusually large, and it has a much larger window for headshots.
+Uncharged headshots deal 150 damage, allowing you to kill 5 of the classes with a single well aimed click.
+Fully charged headshots deal 360 damage, killing anything except an overhealed heavy. This only requires 1 second to charge
+Movement speed while drawn is 45%, instead of 27% while scoped with a sniper rifle.
+An unknown, INCREDIBLY rare, but unique gimmick is that huntsman arrows destroy enemy projectiles it collides with.
+Can be ignited by Pyros, or Soldiers/Engineers with Righteous Bison/Pomson. This is overhyped, it only helps if you make a bodyshot, which you shouldn't be doing anyway.
-Pretty useless at long range. Any kills at this range will be infamous "lucksman" shots.
-Fires slightly faster than once every two seconds. Make your shots count, miss once and you're SOL.
-Only carries 13 arrows at a time.
-Reflectable by Pyros, but chances are minimal that you'll be hit by a reflected arrow at anything other than point blank range.
-If drawn for more than 5 seconds, disables headshot and accuracy is lost. Press your alt-fire to ease the bow, and you can ready again.
This is the biggest game changer for snipers. You become a fragile, mobile one-man mankiller. If offensive sniper sounds interesting, this is what you should be using. Note it's hard at first to lead arrows, but practice will make perfect. Remember to draw your arrow when moving around corners. Aim slightly above eye level on flat ground, and when firing at enemies, lead them and aim slightly above their heads. Use corners to your advantage. If you detect a lone enemy approaching, draw your arrow and hide around a corner they'll walk past. As they turn around the corner, give them a headshot from a meter away. Miss once, you lose. This is one of the most notorious weapons in the game, and it is THE weapon for a sniper on the go. The staple set for an offensive sniper is Huntsman + Jarate + Bushwacka.
Huo Long Heater:
+Unique mechanic, can help against spies who aren't very clever.
-Ammo is even more scarce, and the flames are practically useless in most situations as your minigun will chew up anyone in that range anyway.
Not much different here. Natascha and Brass Beast give entirely different playstyles, but this one isn't far different from the stock Minigun. The best use for it is as a defensive Heavy who is guarding Engineer buildings, igniting spies trying to sap or hide. The ammo loss in this case is negligible as dispensers will refill your ammo rapidly. IMPORTANT NOTE: Smart spies know that it is entirely possible to avoid being ignited with a simple hop over the flames. This will only help prevent attacks from cloaked spies hiding in a corner or spies who approach you directly under a disguise. In most cases, a different minigun provides the same effectiveness with a larger pool of ammo.