Some good info on page 4 of this pdf, under Essential Oils.
Here's a description of myrcene from the wiki:
Myrcene yields flavors that were not traditionally considered desirable by European brewers, and noble hops are very low in myrcene. However, many American hop varieties are very high in myrcene; it makes up up to 60% of total oil in Cascade and up to 70% in Amarillo. Also found in some citrus fruits, myrcene lends American hops many of their distinctive flavors.
When added late in, or after, the boil, myrcene adds the intense, pungent aroma associated with American dry-hopped beers. When boiled for longer periods, it yields the characteristic citrus and pine aromas of American craft beer.
Looks like it comes down to personal preference. It sounds like a nice, low risk experiment when dry hopping split fermenters.