I hate to dodge this question but both choices would be problematic. If I had a higher IQ, I'd hardly be able to function around people. As it is I see most of you as dogs, the best of you as bright-eyed simpletons.
And if my penis was any bigger you'd be able to see it from space. Running would be right out and I'd have to get a California king-sized bed just to house the excess dong flesh when it's nappy time.
Seriously, if I was any smarter they'd have to name a building after me by law. They'd call geniuses 'keiths' moving forward.. They'd pay me a stipend not to take the world hostage. I'd be given an honorary title, something like Sir Ivy League the Brain Champion of Smartland.
If my penis was any bigger horses would learn to blush. Vaginas would go, 'Whaaaaaaaaa?' The toilet would have to be redesigned and fashioned from space-age materials to handle the firehose-like pressure of my urine stream. You'd hear a sonic boom whenever I impregnated someone.
That enough? (...I've asked women without putting hardly any in.)
Short Answer: I'm fine just the way I am. I fear if I was a little smarter, I'd be depressed more often, which is something that highly intelligent people often struggle with. I guess I'd pick bigger penis, because, you know, there's always porn.