Frankly speaking, it's very hard to recommend a world, and it's hard to take one's comment as it may not represent the world condition..

But, in case you play solo, world doesnt matter.. in fact all party finder and duty finder are cross world, you can always play with people from the same data center..

What would you like to consider is does double exp worth in long term? Double exp only apply until one of your class reaches lv 60.. based on my experience hitting lv 60 is very easy while enjoying the main story quest.. but of course you are free to choose