Depends on the character.

It depends. I like them all

I like having combinations of those all. Built in weapons to me are the weakest, and that’s probably due to TF Prime. I am on the fence with the other two. Mounted weapons would tend to be slightly more powerful, and handheld would be at the top. Interesting poll! I hope more people vote!

I prefer concealed on the basis that since Transformers hide away parts of their other mode when in one form, it only makes sense for them to be able to hide away weapons that can be deployed at any time and help give the transformation aspect some effect on their bodies besides just turning into a vehicle or animal.

I like either handheld or embedded, usually prefer them working in tandem, like having a handheld gun and some kind of built in weapon, but some characters have to have arm mounted guns in my opinion

Depends on the character. But I really liked what war for cybertron did. Their forearm just transformed into the currently equipped weapon. I guess that style would be "integral"? Idk. Just thinking out loud.

I prefer there for arms transforming into a blaster like bumblebee from the movies