foo(const T& t);
vs
foo(T const& t);
As far as I know, exactly the same. The difference is purely a style thing. From what I can gather the former is a more 'old school' approach, whilst the later is what you might see more often in newer books.
Is there any difference, superficially and/or getting down into the gritty detail?
Is there any reason to choose one over the other, besides sticking to a convention within a code-base?