How should I decide whether to pursue an EASA ATPL or an FAA ATPL?
Both the EASA and FAA ATPL programs are good, I know people who have both and their view is that neither has an intrinsic benefit over the other. The EASA one has more theory in it which most of the ATPLs I know think is worthless, however if you know how to study it's really not that bad. 

The question of which is best for you is who you want to fly for and where their airplanes are registered, as it's the country of registration which defines which ATPL you need, not the location the airplane is in. An FAA ATPL will let you fly US registered (N Register) airplanes anywhere in the world, and an EASA one will let you fly an EASA member's airplane, so most of Europe anywhere in the world. If you want to fly for a US airline you need an FAA one, if you want to fly for a european airline you need an EASA one.