Why does espresso taste different to percolator coffee? I recently switched from percolator coffee to espresso. The taste is noticeably better. I feel as if it is common knowledge that espresso coffee is superior to percolator coffee. Why is it different? What are the scientific reasons for this?
Espresso tastes different than percolator coffee, but not necessarily better.  Espresso extraction produces a more concentrated drink with a different set of compounds that you would get with percolator extraction.  With a shorter extraction time and higher pressure, espresso will have a slightly different set of compounds than you would get from the same coffee with percolation.  

Some people prefer a more concentrated taste, however, some do not (many people think espresso is "too strong" when drank straight, thus the popularity here in the US of mixed espresso drinks).  This doesn't mean it's necessarily better.  Some types of beans are not well suited to espresso extraction and will actually produce a better cup when brewed with other methods.  

All coffee can be benefited or hindered by brew/prep method, but the quality of the bean and it's roast have quite a bit of influence in the matter.  Badly grown, processed and roasted coffee will not magically be made better by espresso extraction.  It might actually end up worse because concentrating it can highlight it's flaws.