Choosing melee for your leader gives you the best growth in defense and hit points

While some of the leader classes also are available to Rank D (or beginner) mercenaries you can hire from level one, a leader will always be stronger than a mercenary of the same type. In general, leaders are said to be about Silkroad Gold as strong as a Rank C mercenary.

Additionally, leaders can go on a special quest at level 100 to obtain a leader-only spell for their class type. This helps distinguish leaders from a mercenary that uses the same weapon. Also, some leader classes are not available from level one to mercenaries, meaning a selection of one of these classes as your leader will give you access to the skills of that mercenary type sooner.

Finally, other leader classes are not accessible to mercenaries at all, so picking that class for your leader is the only way to get access to those spells.

Leader types fit into three categories: melee, ranged, and caster. Each option has benefits and deficits. Choosing melee for your leader gives you the best growth in defense and hit points, which gives you a better chance at surviving.

However, melee characters tend to work best on the front line of your formation, which exposes your character to the most attacks. This can be disastrous in PvP since your whole squad loses if your leader dies.