it is probably heresy to say this on LuLu, but detail is rarely art. It is craft.
Seurat's A Sunday Afternoon on the Island of La Grande Jatte, which is approximately 7x10 feet, is an astounding piece of art, with a tremendous impact as you stand before it. The resolution is approximately 25 dpi (the whole piece has been estimated at 6mp).
Yes, I know. It's not the same. But the art come first. Fine detail usually only plays a supporting role. However, if your art is about the veins in the leaves and not about the trees or the forest, then go for the details.