soldier: DC-15A rifle, grenades, pistol, bacta packs, coric skin
Jet trooper: DC-15A rifle, grenades, flamethrower, jet missles, pistol
Hawk: pilot that drops down troops at the beginning of the game, DC-15s carbine, hawk skin, parachute
ARF sergeant Boomer: Sniper, SC-15s carbine, grenades, stealth, boomer skin, pistol
Sergeant Denal: Jetpack, missles, DC-15s Carbine, fusion cutter, grenades
Sergeant Kano: DC-15A rifle, pistol, grenades, portable shield, pistol
in the conquest you can play as all of them but in campaign you can only play as soldier and jet trooper and one of each the other 4 ranks sticks with you as support apart from hawk who just flies you in.
As kano you can call for troops to back you up and as denal you can call for jet troopers. as hawk you get to fly around the map wrecking vultures or zombies from above (yes the second part of the campaign has zombie clones)