My brain hurts

I'd say the one who 'is' stupid.

Someone may have an ulterior motive for acting stupid. (ie faking a persona), and 'acting stupid' implies that they are only being stupid for a reason, not that they can't help it (ie, they have a choice).

One might argue that that type is worse, as they are choosing to be an idiot, but, as I started with, In my opinion the fact that they are even reasoning to decide to be stupid put them higher up on the Brain Chain than someone who is unfortunately fundamentally stupid :L

I suppose my ultimate answer would have to be based on WHY they're acting stupid.

I voted the one who "is" stupid, because by definition, they are stupid. Also, if a person decides to act stupidly, that, in itself, is a stupid decision, making both choices people who "are" stupid. <object class="emojione" data="https://resources.enjin.com/1489581540/themes/core/images/emojione/svg/1f61b.svg?0" type="image/svg+xml" standby=":p">:p</object>

No...

The person who pretends to be dumb is worse, because they feel that they can only be socially accepted if they are not seen as smart, or a stereotypical 'nerd'.

That in itself is a completely stupid thing to think, and since the legitimately stupid person doesn't have a choice, the fake is probably dumber.

You assume thats why that person is acting stupid. There could be plenty of other reasons. What if that person is a slapstick comedian? They act stupid for a living even though most of them are actually pretty intelligent.

ima out stupid youuuuuuu

The one who acts, because they are stupid enough to act stupid.

Personally, being one who acts stupid but is actually not stupid, I would have to say the one who is stupid. I hang out with alot of stupid people and I choose to jump on the stupid wagon because when I act normal they can't seem to have a normal conversation with me and also because sometimes I get tired of being as smart as I am.

shouldn't it say "less intelligent"? ya know...since 'more stupid' is improper. lol