Most powerful board is a purely subjective thing, try and narrow your question down. A question which is as open as having too much to choose from, usually produces an answer which gives either everything or nothing. I certainly cant give everything, though I'll try not too give nothing.
The powerfulness of the board is not only based on the board itself but by the components inserted - and perhaps in some weird way the components inserted are of greater influence than the board itself. Some components and indeed the interaction between the components themselves can either be improved or decreased depending upon the specific task.
It is very unlikely your question will resolve in any general meaningful answer, as the "powerfulness" is not only influenced by the aforementioned, but also by many other things. And those "many other things" can be giving meaning when knowing the criteria.
So in conclusion, the validity and meaningfulness of an answer is proportional with the specificness of the question.