what generally performs best?

what generally performs best?
broadmatch, exact or combinaion with negative words

 

What do you mean perform?

(CTR, conversions, etc)

 

both really

i am selling phones at my site

do i write my add for say [O2 XDA Mini] or "O2 XDA Mini"
to get the best of either click thru or conversion

has anything been proven

 

I think the only thing that's been proven so far is that there's no universal answer. I see varying results - in some cases broad macth performs better than exact match and vice versa. I would suggest that you test each variation, track the results, then run with the winner.