There are four different mechanized combat suits of armour called Javelins that can be worn whenever you take on any of the missions, these are Ranger, Interceptor, Storm, and Colossus. Each of these suits has unique properties such as melee attacks and Ultimate Abilities, and has the capacity to be equipped with up to two pieces of gear, and two weapons once you reach level two. Javelins can also be customised with their effectiveness depending on a player's level.
Below is a chart which you can study to see the damage types and the many abilities available to players for each Javelin type. As you can see from the chart there is no best Javelin suit as they each specialise in different areas. If you had to select one for dealing with Anthem's mobs and laying down high levels of damage fast the best option is the Storm Javelin suit.