Built-in weapons or mounted weapons or combo option - which option

A modular design is always preferable in any situation

Free hands but moddable options for legs/shoulders/forearms/etc.

Combo. Built-in weapons are nice. You need something at all times. But holding guns in your hands is retarded when you could be using hands to strap guns onto yourself or plug them into hardpoints and shit.

A universal standard for this also allows you to jack the weapons of whatever enemies you kill, too, which is badass. Don't like this gun / it got damaged / it ran out of ammo? Pop it out and grab the giant laser out of your enemy.

>>13597991
soo..., omnimech?

>>13597675
Mounted for specialty or large weapons. Built in for general use and small weapons.

The size factor is obvious, internal space is at a premium and packing in ammo tends to make vehicles explode.

The specialty factor assumes that mounted weapons can be mounted or removed in the field. After all, a flamethrower probably won't do well against tanks and sandstorms would do bad things for high energy lasers

Having both is the way to go.

Handheld weapons won't cook your machine's insides from constant use.
Integrated weapons aren't so easily targeted/destroyed/accidentally dropped because they're contained within the machine's protective armored shell.

>>13597675
Basic design -build-in
Specialization- Modular

Matters what universe you are in, if the built in weapons often overheat, get shot or cause damage to mech I would recommend using weapons you can detach from your mech easily. In Gundam I wish more mechs were destroyed via their weapons being destroyed.

>>13597675
Omnitech is the best of both worlds.

>>13598006
Same could be said with guns, hands and triggers. That's the most universal system of all.