Good question. Instinctively I would think it would appear to be more sour as a fully extracted shot, but I have no real evidence for that ;) Something to do with the fact that it seems you extract more of those bitter/sour compounds later in the shot. If youve ever split a shot into three 10ml portions you may know what I mean - the last 10ml is not so pleasant really.
But then, I really enjoy lighter roasted, highly acidic espresso - which some people call sour.
But, yes, the lighter roasts can be spectacular brewed via other methods - syphon, drip filter, plunger etc.