Morat Vanguard bring the usual assortment of line infantry tools staring with a Combirifle, Pistol, and knife and can be upgraded to have an HMG , Light Grenade Launcher and Combi, or Missile Launcher for additional Special Weapons Cost. They also have access to a K1 sniper rifle for special weapons cost, which is fairly unique and offers superior active turn attacks against targets of 7 or higher armor compared to a regular Multi Sniper Rifle. Vanguard Infantry can also make use of the offensive tools of their specialist Forward Observers and the EI hacking device.
In the Morat Sectorial Army they can for a Fireteam: Core dramatically increasing the combat effectiveness of these basic troops
Vanguard have basic armor of 1 and a PH of 12 meaning they are better at dodging than most standard troopers. Forward Observers also have access to Flash Pulse which allows them to use their superior WIP to defend themselves.
This unit has the Morat rule which gives it courage and veteran trooper. As such, they never take guts checks, and ignore the effects of retreat, loss of lieutenant, and isolation.
Morat Forward observers can pick between WIP 13 shots and PH 12 dodges to get out of harms way making them survivable cheap specialists.
Like most basic trooper link teams, access to cheap missile launchers and a five strong link can make for a defensive tool that can stymie some opponents. Additionally, a Light Grenade Launcher in the link can benefit from bonus BS when speculative firing.
Despite their special rule and superior PH stat, Vanguard are like any other infantry and can be easily removed by high BS/Burst shooters, melee experts, or templates weapons. Be sure not to try and isolate them to break a link or shut down a hacker (they ignore the effects of the isolated state) and you should be fine.
Morat links are vulnerable to TO ambushes, templates, or mines as even with a full 5 strong link they have basic stats and no visors.
Vanguard fill the low point cost specialist trooper role. If you want cheap orders Ikadrones, Imetrons, or M drones fill that role. For cheap specialist they share the same point level as Batroids and Seed Soldiers but do not have the same disadvantages of either (they start on the table, they can go prone, they have all kinds of specialists, and they come with a combi rifle for longer range combat).
Once place Vanguard are useful is if you are making use of an aggressive lieutenant option that does not have G: Gnemonica. If placed in loss of lieutenant, the Vanguard's Morat special rule means their orders remain regular, allowing them to be used by other, now irregular, troopers. This can blunt the damage of LoL and help you maintain tempo in a game.
A special note can be made for the Morat EI Hacking Device profile which used to be common place in vanilla lists. This profile has largely been replaced by the Nexus Operative HD. While it does provide a cheap Hacking Device, the profile is out classed by the Nexus operative in most of it's stats.
In the Morat Sectorial army they are a core link choice and not a bad one should you want to run higher end models such as Sogorats, Raichos, or a Haris link. They can get the job done for a reasonable rate.
Vanguard are best left out of harms way unless you specifically plan to leave long range shooters out for ARO. The are well served guarding short approaches or deployed close to their target objectives.
Active Turn Role
Individual vanguard will not be taking an active role unless things have gone very badly, or they are acting as a specialist. As line infantry, they are the definition of common stats and you shouldn't expect them to run the table.
In a Link team, a full 5 strong Vanguard unit can expect to win shoot outs by weight of fire against better opponents when using their HMG or sniper rifle from long range. Such links will look to move up board aggressively to get their specialists into play, killing whatever threatens them along the way.
In a link team Vanguard Missile Launchers can stay far back field and take dangerous ARO shots. Most of the time though, you will be better off dodging long range fire due to your superior PH stat, unless you are in a link team.