Lisa, S.A. v. Mayorga,  C.A. 410, 2009  (Del.  April 20, 2010)

This decision clarifies the effect of where an action is first filed.  When the case is filed first in Delaware, a Delaware court may only dismiss it on the grounds the forum is inconvenient when the defendant can show it will be an "overwhelming hardship" to litigate it in Delaware.

On the other hand, when an action is first filed in a forum other than Delaware, the general rule is to defer to the other jurisdiction and stay or dismiss the second suit filed in Delaware.  While there are numerous exceptions to this general rule, the burden is much less to have the case dismissed.