So an employee is joining our cross-functional team. Can choose either the smartest, nerdiest, a little quiet but very technically capable.

And then there's someone with great personality, chatterbox, knows something about everybody, but average.

Depends very much on the position for which you are recruiting!!!!!
....cross functional team???.....great personality sounds just fine!!!!

I have been involved in recruitment since 1997.
If your position is sales/customer facing-centric, go for the personality type. Train the guy on the specifics and they usually come out just fine. The jack- of- all- trade thingy really helps them to engage at several levels.

If you are looking for a server room type, the nerd is your guy.

All in all, I favor the personality/chatterbox/jack of all trade types. Their expectations are easier to manage, and they give full notice when they want to quit. If they are mature-ish, they also have definite plan of how long they'll stick with you. The quiet types are hard to motivate, always pass as with something up their sleeves.

When they want to call quits, they just don't show up - and they take with them elements of your I.P.

If the personality candidate has shown genuine interest to learn, don't think twice...

@waP. Interesting perspective. Never thought of it that way. Always thought nerds would be more loyal