They're two quite different disciplines. If your aim is to fly IFR for a living, then concentrate on that. Most airline pilots wouldn't have the VFR navigational skill-set of your average PPL! Believe it or not IFR flying is much easier as most of the work is done for you. If you have the time left to get an FAA IR and 50 hours IFR pic then you are exempt all training for an EASA IR - except that you'll still need some to cover the differences. And if you get your FAA IR somewhere where they don't have adf fitted - then you'll need a lot of training. NDB holds and approaches are probably the hardest thing to get right.